Led lamp and its power source module

ABSTRACT

An LED tube lamp with overvoltage protection capability is provided. The LED tube lamp includes a lamp tube, two external connection terminals, a rectifying circuit, a filtering circuit, an LED module, and a protection circuit. The protection circuit is coupled between two input terminals of the LED module and configured to perform overvoltage protection when determining that a voltage level between the two input terminals of the LED module reaches or is higher than a predefined voltage value, wherein the protection circuit includes a diode and the predefined voltage value is in a range of about 40V to about 600V.

This application is a continuation in part application of U.S. patentapplication Ser. No. 16/721,832, filed Dec. 19, 2019, which is acontinuation application of U.S. patent application Ser. No. 16/256,075,filed Jan. 24, 2019, which is a continuation application of U.S. patentapplication Ser. No. 15/701,211, filed Sep. 11, 2017, which is acontinuation-in-part application of U.S. patent application Ser. No.15/258,471, filed Sep. 7, 2016, which is a continuation-in-partapplication of U.S. patent application Ser. No. 15/211,813, filed Jul.15, 2016, which is a continuation-in-part application of U.S. patentapplication Ser. No. 15/150,458, filed May 10, 2016, which is acontinuation-in-part application of U.S. patent application Ser. No.14/865,387, filed Sep. 25, 2015, the contents of which applications areincorporated herein by reference in their entirety. U.S. patentapplication Ser. No. 15/258,471 is also a continuation-in-partapplication of U.S. patent application Ser. No. 15/211,783, filed Jul.15, 2016, and is a continuation-in-part application of U.S. patentapplication Ser. No. 14/699,138, filed Apr. 29, 2015, the contents ofeach of which are incorporated herein by reference in their entirety.This application claims priority under 35 U.S.C. 119(e) to ChinesePatent Applications Nos.: CN201510104823.3, filed on 2015 Mar. 10;CN201510338027.6, filed on 2015 Jun. 17; CN 201510651572.0, filed on2015 Oct. 10; CN 201610990012.2, filed on 2016 Nov. 10; CN201611090717.5, filed on 2016 Nov. 30; CN 201610043864.0, filed on 2016Jan. 22; CN 201610363805.1, filed on 2016 May 27; and CN 201710307204.3,filed on 2017 May 2, the contents of which priority applications areincorporated herein by reference in their entirety.

In addition, Chinese Patent Application Nos.: CN201420602526.2, filed on2014 Oct. 17, and CN201510155807.7, filed on 2015 Apr. 3 with the StateIntellectual Property Office (SIPO) is also incorporated herein byreference in its entirety.

This application is also a continuation in part application of U.S.patent application Ser. No. 16/691,859, filed Nov. 22, 2019,incorporated by reference in its entirety, which is a continuationapplication of U.S. patent application Ser. No. 16/273,439, filed Feb.12, 2019, incorporated by reference in its entirety, which is acontinuation application of U.S. patent application Ser. No. 15/889,634,filed Feb. 6, 2018, incorporated by reference herein in its entirety,which is a continuation application of U.S. patent application Ser. No.15/386,139, filed Dec. 21, 2016, incorporated by reference herein in itsentirety, which is a continuation-in-part application of U.S. patentapplication Ser. No. 15/055,630, filed Feb. 28, 2016, incorporated byreference herein in its entirety, which claims the benefit of priorityunder 35 U.S.C. § 119 to the following Chinese Patent Applications,filed with the State Intellectual Property Office (SIPO), each of whichis incorporated herein by reference in its entirety: CN201510104823.3,filed on 2015 Mar. 10; CN201510134586.5, filed on 2015 Mar. 26;CN201510133689.X, filed on 2015 Mar. 25; CN201510173861.4, filed on 2015Apr. 14; CN201510193980.6, filed on 2015 Apr. 22; CN201510372375.5,filed on 2015 Jun. 26; CN201510284720.X, filed on 2015 May 29;CN201510338027.6, filed on 2015 Jun. 17; CN201510315636.X, filed on 2015Jun. 10; CN201510406595.5, filed on 2015 Jul. 10; CN201510486115.0,filed on 2015 Aug. 8; CN201510557717.0, filed on 2015 Sep. 6;CN201510595173.7, filed on 2015 Sep. 18; CN201510530110.3, filed on 2015Aug. 26; CN201510680883.X, filed on 2015 Oct. 20; CN201510259151.3,filed on 2015 May 19; CN201510324394.0, filed on 2015 Jun. 12;CN201510373492.3, filed on 2015 Jun. 26; CN201510482944.1, filed on 2015Aug. 7; CN201510499512.1, filed on 2015 Aug. 14; CN201510448220.5, filedon 2015 Jul. 27; CN201510483475.5, filed on 2015 Aug. 8;CN201510555543.4, filed on 2015 Sep. 2; CN201510724263.1, filed on 2015Oct. 29; CN201610050944.9, filed on 2016 Jan. 26; and CN 201510726484.2,filed on 2015 Oct. 30.

In addition, Chinese Patent Application No.: CN201510075925.7, filed on2015 Feb. 12 with the State Intellectual Property Office (SIPO) is alsoincorporated herein by reference in its entirety.

If any terms in this application conflict with terms used in anyapplication(s) to which this application claims priority, or termsincorporated by reference into this application or the application(s) towhich this application claims priority, a construction based on theterms as used or defined in this application should be applied.

BACKGROUND Technical Field

The present disclosure relates to illumination devices, and moreparticularly relates to an LED tube lamp with a detection circuit fordetecting whether the LED tube lamp is being supplied by an incompatibleballast or for regulating the continuity of current to flow through itsLED unit(s) used to emit light, or a protection circuit for providingovervoltage and/or overcurrent protection.

Related Art

LED (light emitting diode) lighting technology is rapidly developing toreplace traditional incandescent and fluorescent lightings. LED tubelamps are mercury-free in comparison with fluorescent tube lamps thatneed to be filled with inert gas and mercury. Thus, it is not surprisingthat LED tube lamps are becoming a highly desired illumination optionamong different available lighting systems used in homes and workplaces,which used to be dominated by traditional lighting options such ascompact fluorescent light bulbs (CFLs) and fluorescent tube lamps.Benefits of LED tube lamps include improved durability and longevity andfar less energy consumption; therefore, when taking into account allfactors, they would typically be considered as a cost effective lightingoption.

Typical LED tube lamps have a lamp tube, a circuit board disposed insidethe lamp tube with light sources being mounted on the circuit board, andend caps accompanying a power supply provided at two ends of the lamptube with the electricity from the power supply transmitted to the lightsources through the circuit board. However, existing LED tube lamps havecertain drawbacks.

First, the typical circuit board is rigid and allows the entire lamptube to maintain a straight tube configuration when the lamp tube ispartially ruptured or broken, and this gives the user a false impressionthat the LED tube lamp remains usable and is likely to cause the user tobe electrically shocked upon handling or installation of the LED tubelamp.

Second, the rigid circuit board is typically electrically connected withthe end caps by way of wire bonding, in which the wires may be easilydamaged and even broken due to any move during manufacturing,transportation, and usage of the LED tube lamp and therefore may disablethe LED tube lamp.

Further, circuit design of current LED tube lamps mostly doesn't providesuitable solutions for complying with relevant certification standardsand for better compatibility with the driving structure using a ballastoriginally for a fluorescent lamp. For example, since there are usuallyno electronic components in a fluorescent lamp, it's fairly easy for afluorescent lamp to be certified under EMI (electromagneticinterference) standards and safety standards for lighting equipment asprovided by Underwriters Laboratories (UL). However, there are aconsiderable number of electronic components in an LED tube lamp, andtherefore consideration of the impacts caused by the layout (structure)of the electronic components is important, resulting in difficulties incomplying with such standards.

Common main types of electrical ballast include instant-start ballastand programmed-start ballast. Electrical ballast typically includes aresonant circuit and is designed to match the loading characteristics ofa fluorescent lamp in driving the fluorescent lamp. For example, forproperly starting a fluorescent lamp, the ballast provides drivingmethods respectively corresponding to the fluorescent lamp working as acapacitive device before emitting light, and working as a resistivedevice upon emitting light. But an LED is a nonlinear component withsignificantly different characteristics from a fluorescent lamp.Therefore, using an LED tube lamp with a ballast impacts the resonantcircuit design of the ballast, which may cause a compatibility problem.Generally, a programmed-start ballast will detect the presence of afilament in a fluorescent lamp, but traditional LED driving circuitscannot support the detection and may cause a failure of the filamentdetection and thus failure of the starting of the LED tube lamp.

Further, a ballast is in effect a current source, and when it acts as apower supply of an LED tube lamp, problems of overvoltage andovercurrent or under voltage and undercurrent are likely to occur,resulting in damaging of electronic components in the LED tube lamp orunstable provision of lighting by the LED tube lamp. An instance of suchproblems may happen when using some models of electronic ballast tosupply an LED tube lamp. When such a ballast model is working normally,the ballast provides a high frequency current conforming to its designrequirement to the LED tube lamp. When such a ballast model isincompatible or (suddenly) operating abnormally, however, the currentoutput by the ballast may be (instantaneously) increased such that anovercurrent condition happens in the LED module or unit (comprisingLEDs) of the LED tube lamp, to cause burning or breaking of the lightstrip (or circuit sheet) of the LED tube lamp on which the LEDs aredisposed. Since an electronic ballast is typically designed to output aconstant current and a relatively high voltage, in seriousovercurrent/overvoltage conditions the gap or break caused in the lightstrip may produce an electric arc and high temperature, which may evenburn and break the lamp tube and the plastic cover of the LED tube lamp.

Further, the driving of an LED uses a DC driving signal, but the drivingsignal for a fluorescent lamp is a low-frequency, low-voltage AC signalas provided by an AC powerline or an inductive ballast, ahigh-frequency, high-voltage AC signal provided by an electronicballast, or even a DC signal provided by a battery for emergencylighting applications. Since the voltages and frequency spectrums ofthese types of signals differ significantly, simply performing arectification to produce the required DC driving signal in an LED tubelamp is typically not competent at achieving the LED tube lamp'scompatibility with traditional driving systems of a fluorescent lamp.

Conventional fluorescent lamps and LED lamps are typically not equippedwith advanced abilities both to regulate their electrical currents forbetter qualities or functions and to be compatible with various types ofballasts avoiding typical needs to find a suitable lamp when thefluorescent or LED lamp is not compatible with a present type ofballast.

Accordingly, the present disclosure and its embodiments are hereinprovided.

SUMMARY

It's specially noted that the present disclosure may actually includeone or more inventions claimed currently or not yet claimed, and foravoiding confusion due to unnecessarily distinguishing between thosepossible inventions at the stage of preparing the specification, thepossible plurality of inventions herein may be collectively referred toas “the (present) invention” herein.

Various embodiments are summarized in this section, and are describedwith respect to the “present invention,” which terminology is used todescribe certain presently disclosed embodiments, whether claimed ornot, and is not necessarily an exhaustive description of all possibleembodiments, but rather is merely a summary of certain embodiments.Certain of the embodiments described below as various aspects of the“present invention” can be combined in different manners to form an LEDtube lamp or a portion thereof. As such, the term “present invention”used in this specification is not intended to limit the claims in anyway or to indicate that any particular embodiment or component isrequired to be included in a particular claim, and is intended to besynonymous with the “present disclosure.”

According to an aspect of the disclosed embodiment, a light emittingdiode (LED) tube lamp configured to receive an external driving signalincludes an LED module for emitting light, the LED module comprising anLED unit comprising an LED; a rectifying circuit for rectifying theexternal driving signal to produce a rectified signal, the rectifyingcircuit having a first output terminal and a second output terminal foroutputting the rectified signal; a filtering circuit connected to theLED module, and configured to provide a filtered signal for the LEDunit; and a protection circuit for providing protection for the LED tubelamp. The protection circuit includes a voltage divider comprising twoelements connected in series between the first and second outputterminals of the rectifying circuit, for producing a signal at aconnection node between the two elements; and a control circuit coupledto the connection node between the two elements, for receiving, anddetecting a state of, the signal at the connection node. The controlcircuit includes or is coupled to a switching circuit coupled to therectifying circuit, and the switching circuit is configured to betriggered on or off by the detected state, upon the external drivingsignal being input to the LED tube lamp, to allow discontinuous currentto flow through the LED unit.

According to another aspect of the disclosed invention, a light emittingdiode (LED) tube lamp configured to receive an external driving signalincludes: an LED module for emitting light, the LED module comprising anLED unit comprising an LED; a rectifying circuit for rectifying theexternal driving signal to produce a rectified signal, the rectifyingcircuit having a first output terminal and a second output terminal foroutputting the rectified signal; a filtering circuit connected to theLED module, and configured to provide a filtered signal for the LEDunit; and a detection circuit coupled between the rectifying circuit andthe LED module. The detection circuit includes a voltage dividercomprising two elements connected in series between the first and secondoutput terminals of the rectifying circuit, for producing a signal at aconnection node between the two elements, a control circuit coupled tothe connection node between the two elements, for receiving, anddetecting a state of, the signal at the connection node. The controlcircuit includes or is coupled to a switching circuit coupled to therectifying circuit, and the detection circuit is configured such thatwhen the external driving signal is input to the LED tube lamp, forpreventing an overcurrent condition the control circuit is triggered bythe detected state to output a signal to a control terminal of theswitching circuit to turn on or conduct the switching circuit, whereinthe conducting state of the switching circuit eventually dims the lightemitted by the LED unit.

According to another aspect of the disclosed embodiments, a lightemitting diode (LED) tube lamp configured to receive an external drivingsignal includes: a lamp tube; a first external connection terminal and asecond external connection terminal coupled to the lamp tube and forreceiving the external driving signal; an LED module for emitting light,the LED module comprising an LED unit comprising an LED; a rectifyingcircuit for rectifying the external driving signal to produce arectified signal, the rectifying circuit having a first output terminaland a second output terminal for outputting the rectified signal; afiltering circuit coupled to the rectifying circuit and the LED module;and a detection circuit coupled between the rectifying circuit and theLED module. The detection circuit includes a voltage divider comprisingtwo elements connected in series between the first and second outputterminals of the rectifying circuit, for producing a fraction voltage ata connection node between the two elements, and a controller coupled tothe connection node between the two elements, for receiving the fractionvoltage at the connection node. The LED tube lamp further includes aconverter circuit coupled between the controller and the LED module, forconverting a signal from the controller or the rectifying circuit into adriving signal for driving the LED module. The controller includes or iscoupled to a switch coupled to the converter circuit, and the detectioncircuit is configured such that when the fraction voltage is in adefined voltage range, the controller regulates the continuity ofcurrent to flow through the LED unit by alternately turning on and offthe switch.

In addition to using the ballast interface circuit or mode determinationcircuit to facilitate the LED tube lamp starting by the electricalballast, other innovations of mechanical structures of the LED tube lampdisclosed herein, such as the LED tube lamp including improvedstructures of a flexible circuit board or a bendable circuit sheet, andsoldering features of the bendable circuit sheet and a printed circuitboard bearing the power supply module of the LED tube lamp, may also beused to improve the stability of power supplying by the ballast and toprovide strengthened conductive path through, and connections between,the power supply module and the bendable circuit sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary exploded view schematically illustrating anexemplary LED tube lamp, according to certain embodiments;

FIG. 2 is a plan cross-sectional view schematically illustrating anexample of an end structure of a lamp tube of an LED tube lamp accordingto certain embodiments;

FIG. 3 is an exemplary plan cross-sectional view schematicallyillustrating an exemplary local structure of the transition region ofthe end of the lamp tube of FIG. 2;

FIG. 4 is a sectional view schematically illustrating an LED light stripthat includes a bendable circuit sheet with ends thereof passing acrossa transition region of a lamp tube of an LED tube lamp to be solderingbonded to the output terminals of the power supply according to anexemplary embodiment;

FIG. 5A is a cross-sectional view schematically illustrating abi-layered structure of a bendable circuit sheet of an LED light stripof an LED tube lamp according to an exemplary embodiment;

FIG. 5B is a top view illustrating an embodiment of laying outbondingpads for diode components on a light strip of an LED tube lamp;

FIG. 5C is a cross-sectional view illustrating the structure in FIG. 5Balong the direction X-X′ shown in FIG. 5B;

FIGS. 5D-5F are views illustrating improved embodiments of laying outbonding pads for diode components on a light strip of an LED tube lamp;

FIG. 5G illustrates a way to reduce incidence of curving of the lightstrip 2 or its consequent problems by adopting a protective layer 2 d;

FIG. 6 is a perspective view schematically illustrating the solderingpad of a bendable circuit sheet of an LED light strip for solderingconnection with a printed circuit board of a power supply of an LED tubelamp according to an exemplary embodiment;

FIG. 7 is a perspective view schematically illustrating a circuit boardassembly composed of a bendable circuit sheet of an LED light strip anda printed circuit board of a power supply according to another exemplaryembodiment;

FIG. 8 is a perspective view schematically illustrating anotherexemplary arrangement of the circuit board assembly of FIG. 7;

FIG. 9 is a perspective view schematically illustrating a bendablecircuit sheet of an LED light strip formed with two conductive wiringlayers according to another exemplary embodiment;

FIG. 10 is a perspective view of an exemplary bendable circuit sheet anda printed circuit board of a power supply soldered to each other,according to certain embodiments;

FIGS. 11 to 13 are diagrams of an exemplary soldering process of abendable circuit sheet and a printed circuit board of a power supply,such as shown in the example of FIG. 10, according to certainembodiments;

FIG. 14A is a block diagram of an exemplary power supply system for anLED tube lamp according to some embodiments;

FIG. 14B is a block diagram of an exemplary power supply system for anLED tube lamp according to some embodiments;

FIG. 14C is a block diagram showing elements of an exemplary LED lampaccording to some embodiments;

FIG. 14D is a block diagram of an exemplary power supply system for anLED tube lamp according to some embodiments;

FIG. 14E is a block diagram showing elements of an LED lamp according tosome embodiments;

FIG. 15A is a schematic diagram of a rectifying circuit according tosome exemplary embodiments;

FIG. 15B is a schematic diagram of a rectifying circuit according tosome exemplary embodiments;

FIG. 15C is a schematic diagram of a rectifying circuit according tosome exemplary embodiments;

FIG. 15D is a schematic diagram of a rectifying circuit according tosome exemplary embodiments;

FIG. 16A is a schematic diagram of a terminal adapter circuit accordingto some exemplary embodiments;

FIG. 16B is a schematic diagram of a terminal adapter circuit accordingto some exemplary embodiments;

FIG. 16C is a schematic diagram of a terminal adapter circuit accordingto some exemplary embodiments;

FIG. 16D is a schematic diagram of a terminal adapter circuit accordingto some exemplary embodiments;

FIG. 17A is a block diagram of a filtering circuit according to someexemplary embodiments;

FIG. 17B is a schematic diagram of a filtering unit according to someexemplary embodiments;

FIG. 17C is a schematic diagram of a filtering unit according to someexemplary embodiments;

FIG. 17D is a schematic diagram of a filtering unit according to someexemplary embodiments;

FIG. 17E is a schematic diagram of a filtering unit according to someexemplary embodiments;

FIG. 18A is a schematic diagram of an LED module according to someexemplary embodiments;

FIG. 18B is a schematic diagram of an LED module according to someexemplary embodiments;

FIG. 18C is a plan view of a circuit layout of an LED module accordingto some embodiments;

FIG. 18D is a plan view of an improved circuit layout method in an LEDmodule applicable to some embodiments;

FIG. 19 is a block diagram of an LED lamp according to some exemplaryembodiments;

FIG. 20A is a block diagram of an LED lamp according to some exemplaryembodiments;

FIG. 20B is a schematic diagram of an anti-flickering circuit accordingto some exemplary embodiments;

FIG. 21A is a block diagram of an LED lamp according to some exemplaryembodiments;

FIG. 21B is a schematic diagram of a mode determination circuit in anLED lamp according to some exemplary embodiments;

FIG. 21C is a schematic diagram of a mode determination circuit in anLED lamp according to some exemplary embodiments;

FIG. 22A is a block diagram of an LED lamp according to some exemplaryembodiments;

FIG. 22B is a block diagram of an LED lamp according to some exemplaryembodiments;

FIG. 22C illustrates an arrangement with a ballast interface circuit inan LED lamp according to some exemplary embodiments;

FIG. 22D is a block diagram of an LED lamp according to some exemplaryembodiments;

FIG. 22E is a block diagram of an LED lamp according to some exemplaryembodiments;

FIG. 22F is a schematic diagram of a ballast interface circuit accordingto some exemplary embodiments;

FIG. 23A is a schematic diagram of a mode determination circuitaccording to some exemplary embodiments;

FIG. 23B is a schematic diagram of an LED tube lamp according to someexemplary embodiments, which includes an embodiment of the modedetermination circuit;

FIG. 23C is a schematic diagram of an LED tube lamp according to someexemplary embodiments, which includes an embodiment of the modedetermination circuit;

FIG. 23D is a schematic diagram of an LED tube lamp according to someexemplary embodiments, which includes a protection circuit for providingovercurrent protection for the switching circuit 2024.

FIG. 24A is a block diagram of an LED tube lamp according to someexemplary embodiments;

FIG. 24B is a schematic diagram of a filament-simulating circuitaccording to some exemplary embodiments;

FIG. 24C is a schematic diagram of a filament-simulating circuitaccording to some exemplary embodiments;

FIG. 25A is a block diagram of an LED tube lamp according to someexemplary embodiments;

FIG. 25B is a schematic diagram of an overvoltage protection (OVP)circuit according to an exemplary embodiment;

FIG. 25C is a schematic diagram of an OVP circuit according to anexemplary embodiment;

FIG. 26A is a block diagram of an LED lamp according to someembodiments;

FIG. 26B is a schematic diagram of a protection circuit according tosome embodiments;

FIG. 27 is a schematic circuit diagram of an LED tube lamp according tosome embodiments including a protection/detection circuit 760;

FIG. 28A is a block diagram of a driving circuit according to someembodiments;

FIG. 28B is a schematic diagram of a driving circuit according to someembodiments;

FIG. 28C is a schematic diagram of a driving circuit according to someembodiments;

FIG. 28D is a schematic diagram of a driving circuit according to someembodiments;

FIG. 28E is a schematic diagram of a driving circuit according to someembodiments;

FIG. 28F is a block diagram of a driving circuit according to someembodiments;

FIG. 28G is a graph illustrating the relationship between the voltageVin and the objective current lout according to certain embodiments;

FIG. 29A is a schematic diagram of a mode switching circuit in an LEDlamp according to some embodiments;

FIG. 29B is a schematic diagram of a mode switching circuit in an LEDlamp according to some embodiments;

FIG. 29C is a schematic diagram of a mode switching circuit in an LEDlamp according to some embodiments;

FIG. 29D is a schematic diagram of a mode switching circuit in an LEDlamp according to some embodiments;

FIG. 29E is a schematic diagram of a mode switching circuit in an LEDlamp according to some embodiments;

FIG. 29F is a schematic diagram of a mode switching circuit in an LEDlamp according to some embodiments;

FIG. 29G is a schematic diagram of a mode switching circuit in an LEDlamp according to some embodiments; and

FIG. 29H is a schematic diagram of a mode switching circuit in an LEDlamp according to some embodiments.

DETAILED DESCRIPTION

The present disclosure provides a novel LED tube lamp, and also providessome features that can be used in LED lamps that are not LED tube lamps.The present disclosure will now be described in the followingembodiments with reference to the drawings. The following descriptionsof various implementations are presented herein for purpose ofillustration and giving examples only. This invention is not intended tobe exhaustive or to be limited to the precise form disclosed. Theseexample embodiments are just that—examples—and many implementations andvariations are possible that do not require the details provided herein.It should also be emphasized that the disclosure provides details ofalternative examples, but such listing of alternatives is notexhaustive. Furthermore, any consistency of detail between variousexamples should not be interpreted as requiring such detail—it isimpracticable to list every possible variation for every featuredescribed herein. The language of the claims should be referenced indetermining the requirements of the invention.

In the drawings, the size and relative sizes of components may beexaggerated for clarity. Like numbers refer to like elements throughout.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items and may beabbreviated as “/”.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers, or steps, these elements, components, regions, layers, and/orsteps should not be limited by these terms. Unless the context indicatesotherwise, these terms are only used to distinguish one element,component, region, layer, or step from another element, component,region, or step, for example as a naming convention. Thus, a firstelement, component, region, layer, or step discussed below in onesection of the specification could be termed a second element,component, region, layer, or step in another section of thespecification or in the claims without departing from the teachings ofthe present invention. In addition, in certain cases, even if a term isnot described using “first,” “second,” etc., in the specification, itmay still be referred to as “first” or “second” in a claim in order todistinguish different claimed elements from each other.

It will be further understood that the terms “comprises” and/or“comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

It will be understood that when an element is referred to as being“connected” or “coupled” to or “on” another element, it can be directlyconnected or coupled to or on the other element or intervening elementsmay be present. In contrast, when an element is referred to as being“directly connected” or “directly coupled,” or “immediately connected”or “immediately coupled” to another element, there are no interveningelements present. Other words used to describe the relationship betweenelements should be interpreted in a like fashion (e.g., “between” versus“directly between,” “adjacent” versus “directly adjacent,” etc.).However, the term “contact,” as used herein refers to a directconnection (i.e., touching) unless the context indicates otherwise.

Embodiments described herein will be described referring to plan viewsand/or cross-sectional views by way of ideal schematic views.Accordingly, the exemplary views may be modified depending onmanufacturing technologies and/or tolerances. Therefore, the disclosedembodiments are not limited to those shown in the views, but includemodifications in configuration formed on the basis of manufacturingprocesses. Therefore, regions exemplified in figures may have schematicproperties, and shapes of regions shown in figures may exemplifyspecific shapes of regions of elements to which aspects of the inventionare not limited.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the figures. It will be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

Terms such as “same,” “equal,” “planar,” or “coplanar,” as used hereinwhen referring to orientation, layout, location, shapes, sizes, amounts,or other measures do not necessarily mean an exactly identicalorientation, layout, location, shape, size, amount, or other measure,but are intended to encompass nearly identical orientation, layout,location, shapes, sizes, amounts, or other measures within acceptablevariations that may occur, for example, due to manufacturing processes.The term “substantially” may be used herein to emphasize this meaning,unless the context or other statements indicate otherwise. For example,items described as “substantially the same,” “substantially equal,” or“substantially planar,” may be exactly the same, equal, or planar, ormay be the same, equal, or planar within acceptable variations that mayoccur, for example, due to manufacturing processes.

Terms such as “about” or “approximately” may reflect sizes,orientations, or layouts that vary only in a small relative manner,and/or in a way that does not significantly alter the operation,functionality, or structure of certain elements. For example, a rangefrom “about 0.1 to about 1” may encompass a range such as a 0%-5%deviation around 0.1 and a 0% to 5% deviation around 1, especially ifsuch deviation maintains the same effect as the listed range.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present application, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

As used herein, items described as being “electrically connected” areconfigured such that an electrical signal can be passed from one item tothe other. Therefore, a passive electrically conductive component (e.g.,a wire, pad, internal electrical line, etc.) physically connected to apassive electrically insulating component (e.g., a prepreg layer of aprinted circuit board, an electrically insulating adhesive connectingtwo devices, an electrically insulating under fill or mold layer, etc.)is not electrically connected to that component. Moreover, items thatare “directly electrically connected,” to each other are electricallyconnected through one or more conductive components, such as, forexample, wires, pads, internal electrical lines, etc. As such, directlyelectrically connected components do not include components electricallyconnected through elements such as resistors, capacitors, inductors,transistors or diodes. Two immediately adjacent conductive componentsmay be described as directly electrically connected and directlyphysically connected. Also in this disclosure, ballast-compatiblecircuit may also be referred to herein as a ballast interface circuit,as it serves as an interface between an electrical ballast and an LEDlighting module (or LED module) of an LED lamp.

Referring to FIG. 1 and FIG. 2, a glass made lamp tube of an LED tubelamp according to an exemplary embodiment of the present invention hasstructure-strengthened end regions described as follows. The glass madelamp tube 1 includes a main body region 102, two rear end regions 101(or just end regions 101) respectively formed at two ends of the mainbody region 102, and end caps 3 that respectively sleeve the rear endregions 101. The outer diameter of at least one of the rear end regions101 is less than the outer diameter of the main body region 102. In theembodiment of FIGS. 1 and 2, the outer diameters of the two rear endregions 101 are less than the outer diameter of the main body region102. In addition, the surface of the rear end region 101 may be parallelto the surface of the main body region 102 in a cross-sectional view.Specifically, in some embodiments, the glass made lamp tube 1 isstrengthened at both ends, such that the rear end regions 101 are formedto be strengthened structures. In certain embodiments, the rear endregions 101 with strengthened structure are respectively sleeved withthe end caps 3, and the outer diameters of the end caps 3 and the mainbody region 102 have little or no differences. For example, the end caps3 may have the same or substantially the same outer diameters as that ofthe main body region 102 such that there is no gap between the end caps3 and the main body region 102. In this way, a supporting seat in apacking box for transportation of the LED tube lamp contacts not onlythe end caps 3 but also the lamp tube 1 and makes uniform the loadingson the entire LED tube lamp to avoid situations where only the end caps3 are forced, therefore preventing breakage at the connecting portionbetween the end caps 3 and the rear end regions 101 due to stressconcentration. The quality and the appearance of the product aretherefore improved.

In one embodiment, the end caps 3 and the main body region 102 havesubstantially the same outer diameters. These diameters may have atolerance for example within +/−0.2 millimeter (mm), or in some cases upto +/−1.0 millimeter (mm). Depending on the thickness of the end caps 3,the difference between an outer diameter of the rear end regions 101 andan outer diameter of the main body region 102 can be about 1 mm to about10 mm for typical product applications. In some embodiments, thedifference between the outer diameter of the rear end regions 101 andthe outer diameter of the main body region 102 can be about 2 mm toabout 7 mm.

Referring to FIG. 2, the lamp tube 1 is further formed with a transitionregion 103 between the main body region 102 and the rear end regions101. In one embodiment, the transition region 103 is a curved regionformed to have cambers at two ends to smoothly connect the main bodyregion 102 and the rear end regions 101, respectively. For example, thetwo ends of the transition region 103 may be arc-shaped in across-section view along the axial direction of the lamp tube 1.Furthermore, one of the cambers connects the main body region 102 whilethe other one of the cambers connects the rear end region 101. In someembodiments, the arc angle of the cambers is greater than 90 degreeswhile the outer surface of the rear end region 101 is a continuoussurface in parallel with the outer surface of the main body region 102when viewed from the cross-section along the axial direction of the lamptube. In other embodiments, the transition region 103 can be withoutcurve or arc in shape. In certain embodiments, the length of thetransition region 103 along the axial direction of the lamp tube 1 isbetween about 1 mm to about 4 mm. Upon experimentation, it was foundthat when the length of the transition region 103 along the axialdirection of the lamp tube 1 is less than 1 mm, the strength of thetransition region would be insufficient; when the length of thetransition region 103 along the axial direction of the lamp tube 1 ismore than 4 mm, the main body region 102 would be shorter and thedesired illumination surface would be reduced, and the end caps 3 wouldbe longer and the more materials for the end caps 3 would be needed.

As can be seen in FIG. 2, and in the more detailed closer-up depictionin FIG. 3, in certain embodiments, in the transition region 103, thelamp tube 1 narrows, or tapers to have a smaller diameter when movingalong the length of the lamp tube 1 from the main region 102 to the endregion 101. The tapering/narrowing may occur in a continuous, smoothmanner (e.g., to be a smooth curve without any linear angles). Byavoiding angles, in particular any acute angles, the lamp tube 1 is lesslikely to break or crack under pressure.

Referring to FIG. 3, in certain embodiments, the lamp tube 1 is made ofglass, and has a rear end region 101, a main body region 102, and atransition region 103. The transition region 103 has two arc-shapedcambers at both ends to from an S shape; one camber positioned near themain body region 102 is convex outwardly, while the other camberpositioned near the rear end region 101 is concaved inwardly. Generallyspeaking, the radius of curvature, R1, of the camber/arc between thetransition region 103 and the main body region 102 is smaller than theradius of curvature, R2, of the camber/arc between the transition region103 and the rear end region 101. The ratio R1:R2 may range, for example,from about 1:1.5 to about 1:10, and in some embodiments is moreeffective from about 1:2.5 to about 1:5, and in some embodiments is evenmore effective from about 1:3 to about 1:4. In this way, the camber/arcof the transition region 103 positioned near the rear end region 101 isin compression at outer surfaces and in tension at inner surfaces, andthe camber/arc of the transition region 103 positioned near the mainbody region 102 is in tension at outer surfaces and in compression atinner surfaces. Therefore, the goal of strengthening the transitionregion 103 of the lamp tube 1 is achieved. As can be seen in FIG. 3, thetransition region 103 is formed by two curves at both ends, wherein onecurve is toward inside of the light tube 1 and the other curve is towardoutside of the light tube 1. For example, one curve closer to the mainbody region 102 is convex from the perspective of an inside of the lamptube 1 and one curve closer to the end region 101 is concave from theperspective of an inside of the lamp tube 1. The transition region 103of the lamp tube 1 in one embodiment may include only smooth curves, andmay not include any angled surface portions.

Taking the standard specification for a T8 lamp as an example, the outerdiameter of the rear end region 101 is configured to be between about20.9 mm to about 23 mm. An outer diameter of the rear end region 101being less than 20.9 mm would be too small to fittingly insert the powersupply into the lamp tube 1. The outer diameter of the main body region102 is in some embodiments configured to be between about 25 mm to about28 mm. An outer diameter of the main body region 102 being less than 25mm would be inconvenient to strengthen the ends of the main body region102 according to known current manufacturing methods, while an outerdiameter of the main body region 102 being greater than 28 mm is notcompliant to the current industrial standard.

Referring to FIG. 4 and FIG. 9, an LED tube lamp in accordance with anexemplary embodiment includes a lamp tube 1, which may be formed ofglass and may be referred to herein as a glass lamp tube 1; two end capsrespectively disposed at two ends of the glass lamp tube 1; a powersupply 5; and an LED light strip 2 disposed inside the glass lamp tube1. For example, the end cap and the lamp tube are connected to eachother in an adhesive manner such that there is no gap between the endcap and the lamp tube or there are extremely small gaps between the endcap and the lamp tube. The glass lamp tube 1 extending in a firstdirection along a length of the glass lamp tube 1 includes a main bodyregion, a rear end region, and a transition region connecting the mainbody region and the rear end region, wherein the main body region andthe rear end region are substantially parallel. As shown in theembodiment of FIG. 4, the bendable circuit sheet 2 (as an embodiment ofthe light strip 2) passes through a transition region to be soldered ortraditionally wire-bonded with the power supply 5, and then the end capof the LED tube lamp is adhered to the transition region, respectivelyto form a complete LED tube lamp. As discussed herein, a transitionregion of the lamp tube refers to regions outside a central portion ofthe lamp tube and inside terminal ends of the lamp tube. For example, acentral portion of the lamp tube may have a constant diameter, and eachtransition region between the central portion and a terminal end of thelamp tube may have a changing diameter (e.g., at least part of thetransition region may become more narrow moving in a direction from thecentral portion to the terminal end of the lamp tube). End capsincluding the power supply may be disposed at the terminal ends of thelamp tube, and may cover part of the transition region.

With reference to FIG. 5A, in this embodiment, the LED light strip 2 isfixed by the adhesive sheet 4 to an inner circumferential surface of thelamp tube 1, so as to increase the light illumination angle of the LEDtube lamp and broaden the viewing angle to be greater than 330 degrees.

In one embodiment, the inner peripheral surface or the outercircumferential surface of the glass made lamp tube 1 is coated with anadhesive film such that the broken pieces are adhered to the adhesivefilm when the glass made lamp tube is broken. Therefore, the lamp tube 1would not be penetrated to form a through hole connecting the inside andoutside of the lamp tube 1 and this helps prevent a user from touchingany charged object inside the lamp tube 1 to avoid electrical shock. Inaddition, in some embodiments, the adhesive film is able to diffuselight and allows the light to transmit such that the light uniformityand the light transmittance of the entire LED tube lamp increases. Theadhesive film can be used in combination with the adhesive sheet 4, aninsulation adhesive sheet, and an optical adhesive sheet to constitutevarious embodiments. As the LED light strip 2 is configured to be abendable circuit sheet, no coated adhesive film is thereby required. Inaddition, in some embodiments, the vacuum degree of the lamp tube 1 maybe below between about 0.001 Pa and about 1 Pa, which can reduce theproblem(s) due to internal dampness in the lamp tube 1.

In some embodiments, the light strip 2 may be an elongated aluminumplate, FR 4 board, or a bendable circuit sheet. When the lamp tube 1 ismade of glass, adopting a rigid aluminum plate or FR4 board would make abroken lamp tube, e.g., broken into two parts, remain a straight shapeso that a user may be under a false impression that the LED tube lamp isstill usable and fully functional, and it is easy for the user to incurelectric shock upon handling or installation of the LED tube lamp.Because of added flexibility and bendability of the flexible substratefor the LED light strip 2, the problem faced by the aluminum plate, FR4board, or conventional 3-layered flexible board having inadequateflexibility and bendability, are thereby addressed. In certainembodiments, a bendable circuit sheet is adopted as the LED light strip2 because such an LED light strip 2 would not allow a ruptured or brokenlamp tube to maintain a straight shape and therefore would instantlyinform the user of the disability of the LED tube lamp to avoid possiblyincurred electrical shock. The following are further descriptions of abendable circuit sheet that may be used as the LED light strip 2.

Referring to FIG. 5A, in one embodiment, the LED light strip 2 includesa bendable circuit sheet having a conductive wiring layer 2 a and adielectric layer 2 b that are arranged in a stacked manner, wherein thewiring layer 2 a and the dielectric layer 2 b have same areas. The LEDlight source 202 is disposed on one surface of the wiring layer 2 a, thedielectric layer 2 b is disposed on the other surface of the wiringlayer 2 a that is away from the LED light sources 202 (e.g., a second,opposite surface from the first surface on which the LED light source202 is disposed). The wiring layer 2 a is electrically connected to thepower supply 5 to carry direct current (DC) signals. Meanwhile, thesurface of the dielectric layer 2 b away from the wiring layer 2 a(e.g., a second surface of the dielectric layer 2 b opposite a firstsurface facing the wiring layer 2 a) is fixed to the innercircumferential surface of the lamp tube 1 by means of the adhesivesheet 4. The portion of the dielectric layer 2 b fixed to the innercircumferential surface of the lamp tube 1 may substantially conform tothe shape of the inner circumferential surface of the lamp tube 1. Thewiring layer 2 a can be a metal layer or a power supply layer includingwires such as copper wires.

In another embodiment, the outer surface of the wiring layer 2 a or thedielectric layer 2 b may be covered with a circuit protective layer madeof an ink with function of resisting soldering and increasingreflectivity. Alternatively, the dielectric layer can be omitted and thewiring layer can be directly bonded to the inner circumferential surfaceof the lamp tube, and the outer surface of the wiring layer 2 a may becoated with the circuit protective layer. Whether the wiring layer 2 ahas a one-layered, or two-layered structure, the circuit protectivelayer can be adopted. In some embodiments, the circuit protective layeris disposed only on one side/surface of the LED light strip 2, such asthe surface having the LED light source 202. In some embodiments, thebendable circuit sheet is a one-layered structure made of just onewiring layer 2 a, or a two-layered structure made of one wiring layer 2a and one dielectric layer 2 b, and thus is more bendable or flexible tocurl when compared with the conventional three-layered flexiblesubstrate (one dielectric layer sandwiched with two wiring layers). As aresult, the bendable circuit sheet of the LED light strip 2 can beinstalled in a lamp tube with a customized shape or non-tubular shape,and fitly mounted to the inner surface of the lamp tube. The bendablecircuit sheet closely mounted to the inner surface of the lamp tube ispreferable in some cases. In addition, using fewer layers of thebendable circuit sheet improves the heat dissipation and lowers thematerial cost.

Nevertheless, the bendable circuit sheet is not limited to beingone-layered or two-layered; in other embodiments, the bendable circuitsheet may include multiple layers of the wiring layers 2 a and multiplelayers of the dielectric layers 2 b, in which the dielectric layers 2 band the wiring layers 2 a are sequentially stacked in a staggeredmanner, respectively. These stacked layers may be between the outermostwiring layer 2 a (with respect to the inner circumferential surface ofthe lamp tube), which has the LED light source 202 disposed thereon, andthe inner circumferential surface of the lamp tube, and may beelectrically connected to the power supply 5. Moreover, in someembodiments, the length of the bendable circuit sheet is greater thanthe length of the lamp tube (not including the length of the two endcaps respectively connected to two ends of the lamp tube), or at leastgreater than a central portion of the lamp tube between two transitionregions (e.g., where the circumference of the lamp tube narrows) oneither end. In one embodiment, the longitudinally projected length ofthe bendable circuit sheet as the LED light strip 2 is larger than thelength of the lamp tube.

The dielectric layer 2 b described above may comprise a polyimide andthus be called a PI layer. The thickness of the PI layer may be, forexample, in the range of 0.05 mm-0.3 mm, and in some embodiments may bein the range of 0.1 mm-0.2 mm. The wiring layer(s) described above istypically a conductive layer, and may be a copper layer or comprisecopper foil. The thickness of the wiring layer may be in the range of 20um-80 um, and in some embodiments may be in the range of 30 um-50 um. Toprevent the copper foil of the wiring layer from oxidizing which mayadversely affect the reliability of the light strip 2, an organic solderability preservative or OSP method may be performed on the copper foil.

Although the light strip or bendable circuit sheet 2 in FIG. 5A as usedin the structure in FIG. 4 can generally meet requirements of electricaland mechanical functions of an LED tube lamp, when mass production oflight strips 2 involves using bonding/mounting/placement equipment ormachine to mount a mass of devices in chip form onto the light strips ofLED tube lamps, for example using the mounting machines to mount LEDlight sources 202 and in some embodiments electrical components (such asdiodes, bridge rectifiers, and capacitors) onto predefined positions ona light strip 2, the deformed/curving parts or areas of the light strip2 are prone or likely to cause abnormalities (such as welding defects;undesirable displacement; nonwetting; poor contact) of those chipdevices close to the curving parts. Such problems are more common inlight strips each including only one conductive layer.

Testing has revealed that end regions at two terminals of the lightstrip 2 where electrical/electronic components in chip form would bemounted are more likely to curve or be deformed, because such portionsof the light strip 2 suffer larger stress and are therefore susceptibleto curving, which then is likely to cause the above abnormalities ofthose chip devices mounted on those portions. For example, referring toFIG. 5B, which is a top view illustrating an embodiment of laying outbonding pads for diode components on a light strip 2 of an LED tubelamp, and FIG. 5C, which is a cross-sectional view illustrating thestructure in FIG. 5B along the direction X-X′ shown in FIG. 5B but notshowing the pads, since only a first portion (referred to as a spacingportion or an open portion) of the PI layer 2 b (sometimes covered by anink layer) between the two bonding pads 2 p for (two terminals of) diodeD1 (or diode D2) is not covered by a conductive or copper layer 2 a,stress suffered by only this portion of the PI layer 2 b is differentand larger than when the portion of the PI layer 2 b is combined orcoated with a conductive layer, and therefore this portion of the PIlayer 2 b is prone to curve or be deformed. It's noted that a bondingpad may be for example a soldering pad, and may be a chip pad for adevice in chip form to be mounted/attached thereon. The bonding pad maybe, for example, a thin conductive material having a substantially flatsurface. Referring still to FIGS. 5B-5C, in this embodiment, the uppersurface of the conductive layer 2 a except for its portions covered bythe bonding pads 2 p may be covered by an ink layer (not shown), and thebottom surface of the conductive layer 2 a is covered by or coated witha dielectric layer 2 b.

Some ways to prevent, or reduce incidence of, such problems aredescribed as follows. FIGS. 5D-5F are views illustrating improvedembodiments of laying out bonding pads for diode components on a lightstrip of an LED tube lamp. Compared to the way of laying out the bondingpads illustrated in FIGS. 5B-5C, the way of laying out the bonding padsillustrated in FIG. 5D is different in that mounting positions of thetwo pads for diode D1 on the light strip 2 are shifted or translated inrelation to mounting positions of the two pads for diode D2 (e.g.,shifted along a lengthwise direction of the LED light strip). Since thepads for diodes D1 and D2 are disposed on or over the conductive layer 2a of the light strip 2, and mechanical strength of the conductive layer2 a is typically very different from that of the dielectric or PI layer2 b, looking in the transverse direction indicated by the arrow in FIG.5D, stress suffered by the spacing portion of the PI layer 2 b betweenthe two pads 2 p for each diode D1/D2 will be limited by the presence ofa portion of the conductive layer 2 a underlying a pad 2 p for the otherdiode D2/D1, so the stress suffered by the spacing portions of the PIlayer 2 b between the two pads 2 p for diodes D1/D2 in FIG. 5D will beless than the case in FIG. 5B. The reduced stress suffered reducesincidence of curving or deforming of the light strip 2, and thusincreases the yield rate of mounted/attached devices in chip form.

Turning to FIG. 5E illustrating another embodiment, compared to the wayof laying out the bonding pads illustrated in FIGS. 5B-5C, althoughmounting positions of the two pads for diode D1 on the light strip 2 inFIG. 5E are not shifted in relation to mounting positions of the twopads for diode D2, two portions of the conductive layer 2 a are disposedrespectively adjacent to the two right terminal pads for diodes D1 andD2, and disposed over (at least part of) the spacings respectivelybetween the two pads 2 p for diode D1 and between the two pads 2 p fordiode D2. The two portions of the conductive layer 2 a may comprisecopper and be reserved in planning the layout of the conductive layer 2a. In view of the difference in mechanical strength between theconductive layer 2 a and the dielectric layer 2 b, each in-betweenportion of the conductive layer 2 a between the two pads 2 p for eachdiode results in less stress suffered by the spacing portion of the PIlayer 2 b between the two pads 2 p for each diode in FIG. 5E (e.g., thespacing portion may be smaller such that the left edges of theconductive wiring layer 2 a extend further and do not align with theleft edges of the two right pads 2 p, and therefore stress may bereduced). Therefore the less stress suffered reduces incidence ofcurving of the light strip 2, and thus increases the yield rate ofmounted/attached devices in chip form.

Turning to FIG. 5F illustrating another embodiment, similar to the wayof laying out the bonding pads illustrated in FIGS. 5B-5C, mountingpositions of the two pads for diode D1 on the light strip 2 in FIG. 5Fare not shifted in relation to mounting positions of the two pads fordiode D2. But compared to the way of laying out the bonding padsillustrated in FIG. 5E, the way of laying out the bonding padsillustrated in FIG. 5F is different in that two portions of theconductive layer 2 a are disposed respectively adjacent to the leftterminal pad 2 p and the right terminal pad 2 p for diodes D1 and D2respectively, and disposed over (at least part of) the spacingsrespectively between the two pads 2 p for diode D1 and between the twopads 2 p for diode D2. Again in view of the difference in mechanicalstrength between the conductive layer 2 a and the dielectric layer 2 b,each in-between portion of the conductive layer 2 a between the two pads2 p for each diode results in less stress suffered by the spacingportion of the PI layer 2 b between the two pads 2 p for each diode inFIG. 5F (e.g., due to a smaller spacing portion of the PI layer). Soincidence of curving of the light strip 2 is reduced, increasing theyield rate of mounted/attached devices in chip form.

Turning to FIG. 5G illustrating another way to reduce incidence ofcurving of the light strip 2 or its consequent problems, compared to thestructure of the light strip 2 illustrated in FIG. 5C, a protective orsupportive layer 2 d can be adopted and attached/bonded to at least somearea(s) of the bottom surface of the dielectric layer 2 b which area(s)(indirectly) bears, or is below and close to, the bonding pads 2 p towhich devices in chip form are to be mounted. The thickness of theprotective or supportive layer 2 d is preferably shorter than that ofthe rest of the light strip 2, as an excessive thickness of theprotective or supportive layer 2 d may adversely affect the flexibilityof the light strip 2. As another improvement, in addition to or insteadof the supportive layer 2 d, the thickness of some portion(s) of thedielectric layer 2 b which portion(s) (indirectly) bears, or is belowand close to, the bonding pads 2 p may be larger than other portions ofthe dielectric layer 2 b, for example larger by 50%-100% of thethickness of the other portions of the dielectric layer 2 b.

The above embodiments illustrated in FIGS. 5B-5G are described using twopads 2 p for a diode as examples, but it's understood by a person ofordinary skill in the art that in practice the two pads 2 p can insteadbe set for mounting other kinds of electrical devices having two(bonding) terminals, such as a chip capacitor, a chip resistor, or afuse.

Using the examples in the above embodiments illustrated in FIGS. 5D-5Gmay have one or more of the following benefits/advantages: stresssuffered by (portions of) the light strip 2 is reduced; surface evennessof products of the light strip 2 is increased; requirements for a mass,automatic, or batch production of light strips with chip devices mountedthereon can be better met; and/or the mentioned abnormalities of themounted chip devices are avoided or reduced, increasing reliability ofthe finished products of the light strip 2.

Other than using the examples in the above embodiments illustrated inFIGS. 5D-5G to reduce the incidence of curving light strip 2, the way tolay out LEDs 202 or 831 on the conductive or wiring layer(s) of thelight strip 2 in embodiments as illustrated in FIG. 18C below can alsobe improved by applying a technique in embodiments described andillustrated in FIG. 18D below.

Referring to FIG. 4, FIG. 6, and FIG. 9, in some embodiments, the LEDlight strip 2 is disposed inside the glass lamp tube 1 with a pluralityof LED light sources 202 mounted on the LED light strip 2. The LED lightstrip 2 includes a bendable circuit sheet electrically connecting theLED light sources 202 with the power supply 5. The power supply 5 orpower supply module may include various elements for providing power tothe LED light strip 2. For example, the elements may include powerconverters or other circuit elements for providing power to the LEDlight strip 2. For example, the power supply may include a circuit thatconverts or generates power based on a received voltage, in order tosupply power to operate an LED module and the LED light sources 202 ofthe LED tube lamp. A power supply, as described in connection with powersupply 5, may be otherwise referred to as a power conversion module orcircuit or a power module. A power conversion module or circuit, orpower module, may supply or provide power from external signal(s), suchas from an AC power line or from a ballast, to an LED module and the LEDlight sources 202.

In some embodiments, the length of the bendable circuit sheet is largerthan the length of the glass lamp tube 1, and the bendable circuit sheethas a first end and a second end opposite to each other along the firstdirection, and at least one of the first and second ends of the bendablecircuit sheet is bent away from the glass lamp tube 1 to form a freelyextending end portion 21 along a longitudinal direction of the glasslamp tube 1. The freely extendable end portion 21 is an integral portionof the bendable circuit sheet 2. In some embodiments, if two powersupplies 5 are adopted, then the other of the first and second endsmight also be bent away from the glass lamp tube 1 to form anotherfreely extending end portion 21 along the longitudinal direction of theglass lamp tube 1. The freely extending end portion 21 is electricallyconnected to the power supply 5. Specifically, in some embodiments, thepower supply 5 has soldering pads “a” which are capable of beingsoldered with the soldering pads “b” of the freely extending end portion21 by soldering material “g”.

Referring to FIG. 9, in one embodiment, the LED light strip 2 includes abendable circuit sheet having in sequence a first wiring layer 2 a, adielectric layer 2 b, and a second wiring layer 2 c. The thickness ofthe second wiring layer 2 c (e.g., in a direction in which the layers 2a through 2 c are stacked) is greater than that of the first wiringlayer 2 a, and the length of the LED light strip 2 is greater than thatof the lamp tube 1, or at least greater than a central portion of thelamp tube between two transition regions (e.g., where the circumferenceof the lamp tube narrows) on either end. The end region of the lightstrip 2 extending beyond the end portion of the lamp tube 1 withoutdisposition of the light source 202 (e.g., an end portion without lightsources 202 disposed thereon) may be formed with two separate throughholes 203 and 204 to respectively electrically communicate the firstwiring layer 2 a and the second wiring layer 2 c. The through holes 203and 204 are not communicated to each other to avoid short.

In this way, the greater thickness of the second wiring layer 2 c allowsthe second wiring layer 2 c to support the first wiring layer 2 a andthe dielectric layer 2 b, and meanwhile allow the LED light strip 2 tobe mounted onto the inner circumferential surface without being liableto shift or deform, and thus the yield rate of product can be improved.In addition, the first wiring layer 2 a and the second wiring layer 2 care in electrical communication such that the circuit layout of thefirst wiring later 2 a can be extended downward to the second wiringlayer 2 c to reach the circuit layout of the entire LED light strip 2.Moreover, since the land for the circuit layout becomes two-layered, thearea of each single layer and therefore the width of the LED light strip2 can be reduced such that more LED light strips 2 can be put on aproduction line to increase productivity.

Furthermore, the first wiring layer 2 a and the second wiring layer 2 cof the end region of the LED light strip 2 that extends beyond the endportion of the lamp tube 1 without disposition of the light source 202can be used to accomplish the circuit layout of a power supply module sothat the power supply module can be directly disposed on the bendablecircuit sheet of the LED light strip 2.

The power supply 5 according to some embodiments of the presentinvention can be formed on a single printed circuit board provided witha power supply module as depicted for example in in FIG. 4.

In still another embodiment, the connection between the power supply 5and the LED light strip 2 may be accomplished via tin soldering, rivetbonding, or welding. One way to secure the LED light strip 2 is toprovide the adhesive sheet 4 at one side thereof and adhere the LEDlight strip 2 to the inner surface of the lamp tube 1 via the adhesivesheet 4. Two ends of the LED light strip 2 can be either fixed to ordetached from the inner surface of the lamp tube 1.

In case where two ends of the LED light strip 2 are fixed to the innersurface of the lamp tube and that the LED light strip 2 is connected tothe power supply 5 via wire-bonding, any movement in subsequenttransportation is likely to cause the bonded wires to break. Therefore,a useful option for the connection between the light strip 2 and thepower supply 5 could be soldering. Specifically, referring to FIG. 4,the ends of the LED light strip 2 including the bendable circuit sheetare arranged to pass over the strengthened transition region and bedirectly solder bonded to an output terminal of the power supply 5. Thismay improve the product quality by avoiding using wires and/or wirebonding.

Referring to FIG. 6, an output terminal of the printed circuit board ofthe power supply 5 may have soldering pads “a” provided with an amountof solder (e.g., tin solder) with a thickness sufficient to later form asolder joint. Correspondingly, the ends of the LED light strip 2 mayhave soldering pads “b”. The soldering pads “a” on the output terminalof the printed circuit board of the power supply 5 are soldered to thesoldering pads “b” on the LED light strip 2 via the tin solder on thesoldering pads “a”. The soldering pads “a” and the soldering pads “b”may be face to face during soldering such that the connection betweenthe LED light strip 2 and the printed circuit board of the power supply5 is the most firm. However, this kind of soldering typically includesthat a thermo-compression head presses on the rear surface of the LEDlight strip 2 and heats the tin solder, i.e. the LED light strip 2intervenes between the thermo-compression head and the tin solder, andtherefore may easily cause reliability problems.

Referring again to FIG. 6, two ends of the LED light strip 2 detachedfrom the inner surface of the lamp tube 1 are formed as freely extendingportions 21, while most of the LED light strip 2 is attached and securedto the inner surface of the lamp tube 1. One of the freely extendingportions 21 has the soldering pads “b” as mentioned above. Uponassembling of the LED tube lamp, the freely extending end portions 21along with the soldered connection of the printed circuit board of thepower supply 5 and the LED light strip 2 would be coiled, curled up ordeformed to be fittingly accommodated inside the lamp tube 1. When thebendable circuit sheet of the LED light strip 2 includes in sequence thefirst wiring layer 2 a, the dielectric layer 2 b, and the second wiringlayer 2 c as shown in FIG. 9, the freely extending end portions 21 canbe used to accomplish the connection between the first wiring layer 2 aand the second wiring layer 2 c and arrange the circuit layout of thepower supply 5.

In this embodiment, during the connection of the LED light strip 2 andthe power supply 5, the soldering pads “b” and the soldering pads “a”and the LED light sources 202 are on surfaces facing toward the samedirection and the soldering pads “b” on the LED light strip 2 are eachformed with a through hole such that the soldering pads “b” and thesoldering pads “a” communicate with each other via the through holes.When the freely extending end portions 21 are deformed due tocontraction or curling up, the soldered connection of the printedcircuit board of the power supply 5 and the LED light strip 2 exerts alateral tension on the power supply 5. Furthermore, the solderedconnection of the printed circuit board of the power supply 5 and theLED light strip 2 also exerts a downward tension on the power supply 5when compared with the situation where the soldering pads “a” of thepower supply 5 and the soldering pads “b” of the LED light strip 2 areface to face. This downward tension on the power supply 5 comes from thetin solders inside the through holes and forms a stronger and moresecure electrical connection between the LED light strip 2 and the powersupply 5. As described above, the freely extending portions 21 may bedifferent from a fixed portion of the LED light strip 2 in that theyfixed portion may conform to the shape of the inner surface of the lamptube 1 and may be fixed thereto, while the freely extending portion 21may have a shape that does not conform to the shape of the lamp tube 1.For example, there may be a space between an inner surface of the lamptube 1 and the freely extending portion 21. As shown in FIG. 6, thefreely extending portion 21 may be bent away from the lamp tube 1.

The through hole communicates the soldering pad “a” with the solderingpad “b” so that the solder (e.g., tin solder) on the soldering pads “a”passes through the through holes and finally reach the soldering pads“b”. A smaller through hole would make it difficult for the tin solderto pass. The tin solder accumulates around the through holes uponexiting the through holes and condenses to form a solder ball “g” with alarger diameter than that of the through holes upon condensing. Such asolder ball “g” functions as a rivet to further increase the stabilityof the electrical connection between the soldering pads “a” on the powersupply 5 and the soldering pads “b” on the LED light strip 2.

Referring to FIGS. 7 and 8, in another embodiment, the LED light strip 2and the power supply 5 may be connected by utilizing a circuit boardassembly 25 instead of solder bonding. The circuit board assembly 25 hasa long circuit sheet 251 and a short circuit board 253 that are adheredto each other with the short circuit board 253 being adjacent to theside edge of the long circuit sheet 251. The short circuit board 253 maybe provided with power supply module 250 to form the power supply 5. Theshort circuit board 253 is stiffer or more rigid than the long circuitsheet 251 to be able to support the power supply module 250.

The long circuit sheet 251 may be the bendable circuit sheet of the LEDlight strip including a wiring layer 2 a as shown in FIG. 5A. The wiringlayer 2 a of the long circuit sheet 251 and the power supply module 250may be electrically connected in various manners depending on the demandin practice. As shown in FIG. 7, the power supply module 250 and thelong circuit sheet 251 having the wiring layer 2 a on one surface are onthe same side of the short circuit board 253 such that the power supplymodule 250 is directly connected to the long circuit sheet 251. As shownin FIG. 8, alternatively, the power supply module 250 and the longcircuit sheet 251 including the wiring layer 2 a on one surface are onopposite sides of the short circuit board 253 such that the power supplymodule 250 is directly connected to the short circuit board 253 andindirectly connected to the wiring layer 2 a of the LED light strip 2 byway of the short circuit board 253.

As shown in FIG. 7, in one embodiment, the long circuit sheet 251 andthe short circuit board 253 are adhered together first, and the powersupply module 250 is subsequently mounted on the wiring layer 2 a of thelong circuit sheet 251 serving as the LED light strip 2. The longcircuit sheet 251 of the LED light strip 2 herein is not limited toinclude only one wiring layer 2 a and may further include another wiringlayer such as the wiring layer 2 c shown in FIG. 9. The light sources202 are disposed on the wiring layer 2 a of the LED light strip 2 andelectrically connected to the power supply 5 by way of the wiring layer2 a. As shown in FIG. 8, in another embodiment, the long circuit sheet251 of the LED light strip 2 may include a wiring layer 2 a and adielectric layer 2 b. The dielectric layer 2 b may be adhered to theshort circuit board 253 first and the wiring layer 2 a is subsequentlyadhered to the dielectric layer 2 b and extends to the short circuitboard 253. All these embodiments are within the scope of applying thecircuit board assembly concept of the present invention.

In the above-mentioned embodiments, the short circuit board 253 may havea length generally of about 15 mm to about 40 mm and in some preferableembodiments about 19 mm to about 36 mm, while the long circuit sheet 251may have a length generally of about 800 mm to about 2800 mm and in someembodiments of about 1200 mm to about 2400 mm. A ratio of the length ofthe short circuit board 253 to the length of the long circuit sheet 251ranges from, for example, about 1:20 to about 1:200.

When the ends of the LED light strip 2 are not fixed on the innersurface of the lamp tube 1, the connection between the LED light strip 2and the power supply 5 via soldering bonding would likely not firmlysupport the power supply 5, and it may be necessary to dispose the powersupply 5 inside the end cap. For example, a longer end cap to haveenough space for receiving the power supply 5 may be used. However, thiswill reduce the length of the lamp tube under the prerequisite that thetotal length of the LED tube lamp is fixed according to the productstandard, and may therefore decrease the effective illuminating areas.

Referring to FIG. 10 to FIG. 13, FIG. 10 is a perspective view of abendable circuit sheet 200 and a printed circuit board 420 of a powersupply 400 soldered to each other and FIG. 11 to FIG. 13 are diagrams ofa soldering process of the bendable circuit sheet 200 and the printedcircuit board 420 of the power supply 400. In the embodiment, thebendable circuit sheet 200 and the freely extending end portion 21 havethe same structure. The freely extending end portion 21 comprises theportions of two opposite ends of the bendable circuit sheet 200 and isutilized for being connected to the printed circuit board 420. Thebendable circuit sheet 200 and the power supply 400 are electricallyconnected to each other by soldering. The bendable circuit sheet 200comprises a circuit layer 200 a and a circuit protection layer 200 cover a side of the circuit layer 200 a. Moreover, the bendable circuitsheet 200 comprises two opposite surfaces which are a first surface 2001and a second surface 2002. The first surface 2001 is the one on thecircuit layer 200 a and away from the circuit protection layer 200 c.The second surface 2002 is the other one on the circuit protection layer200 c and away from the circuit layer 200 a. Several LED light sources202 are disposed on the first surface 2001 and are electricallyconnected to circuits of the circuit layer 200 a. The circuit protectionlayer 200 c is made by polyimide (PI) having less thermal conductivitybut being beneficial to protect the circuits. The first surface 2001 ofthe bendable circuit sheet 200 comprises soldering pads “b”. Solderingmaterial “g” can be placed on the soldering pads “b”. In one embodiment,the bendable circuit sheet 200 further comprises a notch “f”. The notch“f” is disposed on an edge of the end of the bendable circuit sheet 200soldered to the printed circuit board 420 of the power supply 400. Insome embodiments instead of a notch, a hole near the edge of the end ofthe bendable circuit sheet 200 may be used, which may thus provideadditional contact material between the printed circuit board 420 andthe bendable circuit sheet 200, thereby providing a stronger connection.The printed circuit board 420 comprises a power circuit layer 420 a andsoldering pads “a”. Moreover, the printed circuit board 420 comprisestwo opposite surfaces which are a first surface 421 and a second surface422. The second surface 422 is the one on the power circuit layer 420 a.The soldering pads “a” are respectively disposed on the first surface421 and the second surface 422. The soldering pads “a” on the firstsurface 421 are corresponding to those on the second surface 422.Soldering material “g” can be placed on the soldering pad “a”. In oneembodiment, considering the stability of soldering and the optimizationof automatic process, the bendable circuit sheet 200 is disposed belowthe printed circuit board 420 (their relative positions are shown inFIG. 11). That is to say, the first surface 2001 of the bendable circuitsheet 200 is connected to the second surface 422 of the printed circuitboard 420. Also, as shown, the soldering material “g” can contact,cover, and be soldered to a top surface of the bendable circuit sheet200 (e.g., first surface 2001), end side surfaces of soldering pads “a,”soldering pad “b,” and power circuit layer 420 a formed at an edge ofthe printed circuit board 420, and a top surface of soldering pad “a” atthe top surface 421 of the printed circuit board 420. In addition, thesoldering material “g” can contact side surfaces of soldering pads “a,”soldering pad “b,” and power circuit layer 420 a formed at a hole in theprinted circuit board 420 and/or at a hole or notch in bendable circuitsheet 200. The soldering material may therefore form a bump-shapedportion covering portions of the bendable circuit sheet 200 and theprinted circuit board 420, and a rod-shaped portion passing through theprinted circuit board 420 and through a hole or notch in the bendablecircuit sheet 200. The two portions (e.g., bump-shaped portion androd-shaped portion) may serve as a rivet, for maintaining a strongconnection between the bendable circuit sheet 200 and the printedcircuit board 420.

As shown in FIG. 12 and FIG. 13, in an exemplary soldering process ofthe bendable circuit sheet 200 and the printed circuit board 420, thecircuit protection layer 200 c of the bendable circuit sheet 200 isplaced on a supporting table 42 (i.e., the second surface 2002 of thebendable circuit sheet 200 contacts the supporting table 42) in advanceof soldering. The soldering pads “a” on the second surface 422 of theprinted circuit board 420 directly sufficiently contact the solderingpads “b” on the first surface 2001 of the bendable circuit sheet 200.And then a heating head 41 presses on a portion of the solderingmaterial “g” where the bendable circuit sheet 200 and the printedcircuit board 420 are soldered to each other. When soldering, thesoldering pads “b” on the first surface 2001 of the bendable circuitsheet 200 directly contact the soldering pads “a” on the second surface422 of the printed circuit board 420, and the soldering pads “a” on thefirst surface 421 of the printed circuit board 420 contact the solderingmaterial “g,” which is pressed on by heating head 41. Under thecircumstances, the heat from the heating heads 41 can directly transmitthrough the soldering pads “a” on the first surface 421 of the printedcircuit board 420 and the soldering pads “a” on the second surface 422of the printed circuit board 420 to the soldering pads “b” on the firstsurface 2001 of the bendable circuit sheet 200. The transmission of theheat between the heating heads 41 and the soldering pads “a” and “b”won't be affected by the circuit protection layer 200 c which hasrelatively less thermal conductivity, since the circuit protection layer200 c is not between the heating head 41 and the circuit layer 200a.Consequently, the efficiency and stability regarding the connectionsand soldering process of the soldering pads “a” and “b” of the printedcircuit board 420 and the bendable circuit sheet 200 can be improved. Asshown in the exemplary embodiment of FIG. 12, the printed circuit board420 and the bendable circuit sheet 200 are firmly connected to eachother by the soldering material “g”. Components between the virtual lineM and the virtual line N of FIG. 12 from top to bottom are the solderingpads “a” on the first surface 421 of printed circuit board 420, thepower circuit layer 420 a, the soldering pads “a” on the second surface422 of printed circuit board 420, the soldering pads “b” on the firstsurface 2001 of bendable circuit sheet 200, the circuit layer 200 a ofthe bendable circuit sheet 200, and the circuit protection layer 200 cof the bendable circuit sheet 200. The connection of the printed circuitboard 420 and the bendable circuit sheet 200 are firm and stable. Thesoldering material “g” may extend higher than the soldering pads “a” onthe first surface 421 of printed circuit board 420 and may fill in otherspaces, as described above.

In other embodiments, an additional circuit protection layer (e.g., PIlayer) can be disposed over the first surface 2001 of the circuit layer200 a. For example, the circuit layer 200 a may be sandwiched betweentwo circuit protection layers, and therefore the first surface 2001 ofthe circuit layer 200 a can be protected by the circuit protectionlayer. A part of the circuit layer 200 a (the part having the solderingpads “b”) is exposed for being connected to the soldering pads “a” ofthe printed circuit board 420. Other parts of the circuit layer 200 aare exposed by the additional circuit protection layer so they canconnect to LED light sources 202. Under these circumstances, a part ofthe bottom of the each LED light source 202 contacts the circuitprotection layer on the first surface 2001 of the circuit layer 200 a,and another part of the bottom of the LED light source 202 contacts thecircuit layer 200 a.

According to the exemplary embodiments shown in FIG. 10 to FIG. 13, theprinted circuit board 420 further comprises through holes “h” passingthrough the soldering pads “a”. In an automatic soldering process, whenthe heating head 41 automatically presses the printed circuit board 420,the soldering material “g” on the soldering pads “a” can be pushed intothe through holes “h” by the heating head 41 accordingly, which fits theneed of automatic process.

Next, examples of the circuit design and using of the power supplymodule 250 are described as follows.

FIG. 14A is a block diagram of a power supply system for an LED tubelamp according to an embodiment.

Referring to FIG. 14A, an AC power supply 508 is used to supply an ACsupply signal, and may be an AC powerline with a voltage rating, forexample, of 100-277 volts and a frequency rating, for example, of 50 or60 Hz. A lamp driving circuit 505 receives and then converts the ACsupply signal into an AC driving signal as an external driving signal(external, in that it is external to the LED tube lamp). Lamp drivingcircuit 505 may be for example an electronic ballast used to convert theAC powerline into a high-frequency high-voltage AC driving signal.Common types of electronic ballast include instant-start ballast,programmed-start or rapid-start ballast, etc., which may all beapplicable to the LED tube lamp of the present disclosure. The voltageof the AC driving signal is in some embodiments higher than 300 volts,and is in some embodiments in the range of about 400-700 volts. Thefrequency of the AC driving signal is in some embodiments higher than 10k Hz, and is in some embodiments in the range of about 20 k-50 k Hz. TheLED tube lamp 500 receives an external driving signal and is thus drivento emit light via the LED light sources 202. In one embodiment, theexternal driving signal comprises the AC driving signal from lampdriving circuit 505. In one embodiment, LED tube lamp 500 is in adriving environment in which it is power-supplied at only one end caphaving two conductive pins 501 and 502, which are coupled to lampdriving circuit 505 to receive the AC driving signal. The two conductivepins 501 and 502 may be electrically and physically connected to, eitherdirectly or indirectly, the lamp driving circuit 505. The two conductivepins 501 and 502 may be formed, for example, of a conductive materialsuch as a metal. The conductive pins may have, for example, a protrudingrod-shape, or a ball shape. Conductive pins such as 501 and 502 may begenerally referred to as external connection terminals, for connectingthe LED tube lamp 500 to an external socket. Under such circumstance,conductive pin 501 can be referred to as the first external connectionterminal, and conductive pin 502 can be referred to as the secondexternal connection terminal. The external connection terminals may havean elongated shape, a ball shape, or in some cases may even be flat ormay have a female-type connection for connecting to protruding maleconnectors in a lamp socket. In another embodiment, the numbers of theconductive pins may more than two. For example, the numbers of theconductive pins can vary depending on the needs of the application.

In some embodiments, lamp driving circuit 505 may be omitted and istherefore depicted by a dotted line. In one embodiment, if lamp drivingcircuit 505 is omitted, AC power supply 508 is directly connected topins 501 and 502, which then receive the AC supply signal as an externaldriving signal.

In addition to the above use with a single-end power supply, LED tubelamp 500 may instead be used with a dual-end power supply to one pin ateach of the two ends of an LED lamp tube. FIG. 14B is a block diagram ofa power supply system for an LED tube lamp according to one embodiment.Referring to FIG. 14B, compared to that shown in FIG. 14A, pins 501 and502 are respectively disposed at the two opposite end caps of LED tubelamp 500, forming a single pin at each end of LED tube lamp 500, withother components and their functions being the same as those in FIG.14A.

FIG. 14C is a block diagram showing elements of an LED lamp according toan exemplary embodiment. Referring to FIG. 14C, the power supply module250 of the LED lamp may include a rectifying circuit 510 and a filteringcircuit 520, and may also include some components of an LED lightingmodule 530. Rectifying circuit 510 is coupled to pins 501 and 502 toreceive and then rectify an external driving signal, so as to output arectified signal at output terminals 511 and 512. The external drivingsignal may be the AC driving signal or the AC supply signal describedwith reference to FIGS. 14A and 14B, or may even be a DC signal, whichin some embodiments does not alter the LED lamp of the presentinvention. Filtering circuit 520 is coupled to the first rectifyingcircuit for filtering the rectified signal to produce a filtered signal.For instance, filtering circuit 520 is coupled to terminals 511 and 512to receive and then filter the rectified signal, so as to output afiltered signal at output terminals 521 and 522. LED lighting module 530is coupled to filtering circuit 520, to receive the filtered signal foremitting light. For instance, LED lighting module 530 may include acircuit coupled to terminals 521 and 522 to receive the filtered signaland thereby to drive an LED unit (e.g., LED light sources 202 on an LEDlight strip 2, as discussed above, and not shown in FIG. 14C). Forexample, as described in more detail below, LED lighting module 530 mayinclude a driving circuit coupled to an LED module to emit light.Details of these operations are described in below descriptions ofcertain embodiments.

In some embodiments, although there are two output terminals 511 and 512and two output terminals 521 and 522 in embodiments of these Figs., inpractice the number of ports or terminals for coupling betweenrectifying circuit 510, filtering circuit 520, and LED lighting module530 may be one or more depending on the needs of signal transmissionbetween the circuits or devices.

In addition, the power supply module of the LED lamp described in FIG.14C, and embodiments of the power supply module of an LED lamp describedbelow, may each be used in the LED tube lamp 500 in FIGS. 14A and 14B,and may instead be used in any other type of LED lighting structurehaving two conductive pins used to conduct power, such as LED lightbulbs, personal area lights (PAL), plug-in LED lamps with differenttypes of bases (such as types of PL-S, PL-D, PL-T, PL-L, etc.), etc.

FIG. 14D is a block diagram of a power supply system for an LED tubelamp according to an embodiment. Referring to FIG. 14D, an AC powersupply 508 is used to supply an AC supply signal. A lamp driving circuit505 receives and then converts the AC supply signal into an AC drivingsignal. An LED tube lamp 500 receives an AC driving signal from lampdriving circuit 505 and is thus driven to emit light. In thisembodiment, LED tube lamp 500 is power-supplied at its both end capsrespectively having two pins 501 and 502 and two pins 503 and 504, whichare coupled to lamp driving circuit 505 to concurrently receive the ACdriving signal to drive an LED unit (not shown) in LED tube lamp 500 toemit light. AC power supply 508 may be, e.g., the AC powerline, and lampdriving circuit 505 may be a stabilizer or an electronic ballast. Itshould be noted that different pins or external connection terminalsdescribed throughout this specification may be named as firstpin/external connection terminal, second pin/external connectionterminal, third pin/external connection terminal, etc., for discussionpurposes. Therefore, in some situations, for example, externalconnection terminal 501 may be referred to as a first externalconnection terminal, and external connection terminal 503 may bereferred to as a second external connection terminal. Also, the lamptube may include two end caps respectively coupled to two ends thereof,and the pins may be coupled to the end caps, such that the pins arecoupled to the lamp tube.

FIG. 14E is a block diagram showing components of an LED lamp accordingto an exemplary embodiment. Referring to FIG. 14E, the power supplymodule of the LED lamp includes a rectifying circuit 510, a filteringcircuit 520, and a rectifying circuit 540, and may also include somecomponents of an LED lighting module 530. Rectifying circuit 510 iscoupled to pins 501 and 502 to receive and then rectify an externaldriving signal conducted by pins 501 and 502. Rectifying circuit 540 iscoupled to pins 503 and 504 to receive and then rectify an externaldriving signal conducted by pins 503 and 504. Therefore, the powersupply module of the LED lamp may include two rectifying circuits 510and 540 configured to output a rectified signal at output terminals 511and 512. Filtering circuit 520 is coupled to terminals 511 and 512 toreceive and then filter the rectified signal, so as to output a filteredsignal at output terminals 521 and 522. LED lighting module 530 iscoupled to terminals 521 and 522 to receive the filtered signal andthereby to drive an LED unit (not shown) of LED lighting module 530 toemit light.

The power supply module of the LED lamp in this embodiment of FIG. 14Emay be used in LED tube lamp 500 with a dual-end power supply in FIG.14D. In some embodiments, since the power supply module of the LED lampcomprises rectifying circuits 510 and 540, the power supply module ofthe LED lamp may be used in LED tube lamps 500 with a single-end powersupply in FIGS. 14A and 14B, to receive an external driving signal (suchas the AC supply signal or the AC driving signal described above). Thepower supply module of an LED lamp in this embodiment and otherembodiments herein may also be used with a DC driving signal.

FIG. 15A is a schematic diagram of a rectifying circuit according to anexemplary embodiment. Referring to FIG. 15A, rectifying circuit 610includes rectifying diodes 611, 612, 613, and 614, configured tofull-wave rectify a received signal. Diode 611 has an anode connected tooutput terminal 512, and a cathode connected to pin 502. Diode 612 hasan anode connected to output terminal 512, and a cathode connected topin 501. Diode 613 has an anode connected to pin 502, and a cathodeconnected to output terminal 511. Diode 614 has an anode connected topin 501, and a cathode connected to output terminal 511.

When pins 501 and 502 (generally referred to as terminals) receive an ACsignal, rectifying circuit 610 operates as follows. During the connectedAC signal's positive half cycle, the AC signal is input through pin 501,diode 614, and output terminal 511 in sequence, and later output throughoutput terminal 512, diode 611, and pin 502 in sequence. During theconnected AC signal's negative half cycle, the AC signal is inputthrough pin 502, diode 613, and output terminal 511 in sequence, andlater output through output terminal 512, diode 612, and pin 501 insequence. Therefore, during the connected AC signal's full cycle, thepositive pole of the rectified signal produced by rectifying circuit 610remains at output terminal 511, and the negative pole of the rectifiedsignal remains at output terminal 512. Accordingly, the rectified signalproduced or output by rectifying circuit 610 is a full-wave rectifiedsignal.

When pins 501 and 502 are coupled to a DC power supply to receive a DCsignal, rectifying circuit 610 operates as follows. When pin 501 iscoupled to the anode of the DC supply and pin 502 to the cathode of theDC supply, the DC signal is input through pin 501, diode 614, and outputterminal 511 in sequence, and later output through output terminal 512,diode 611, and pin 502 in sequence. When pin 501 is coupled to thecathode of the DC supply and pin 502 to the anode of the DC supply, theDC signal is input through pin 502, diode 613, and output terminal 511in sequence, and later output through output terminal 512, diode 612,and pin 501 in sequence. Therefore, no matter what the electricalpolarity of the DC signal is between pins 501 and 502, the positive poleof the rectified signal produced by rectifying circuit 610 remains atoutput terminal 511, and the negative pole of the rectified signalremains at output terminal 512.

Therefore, rectifying circuit 610 in this embodiment can output orproduce a proper rectified signal regardless of whether the receivedinput signal is an AC or DC signal.

FIG. 15B is a schematic diagram of a rectifying circuit according to anexemplary embodiment. Referring to FIG. 15B, rectifying circuit 710includes rectifying diodes 711 and 712, configured to half-wave rectifya received signal. Diode 711 has an anode connected to pin 502, and acathode connected to output terminal 511. Diode 712 has an anodeconnected to output terminal 511, and a cathode connected to pin 501.Output terminal 512 may be omitted or grounded depending on actualapplications.

Next, exemplary operation(s) of rectifying circuit 710 is described asfollows.

In one embodiment, during a received AC signal's positive half cycle,the electrical potential at pin 501 is higher than that at pin 502, sodiodes 711 and 712 are both in a cutoff state as being reverse-biased,making rectifying circuit 710 not outputting a rectified signal. Duringa received AC signal's negative half cycle, the electrical potential atpin 501 is lower than that at pin 502, so diodes 711 and 712 are both ina conducting state as being forward-biased, allowing the AC signal to beinput through diode 711 and output terminal 511, and later outputthrough output terminal 512, a ground terminal, or another end of theLED tube lamp not directly connected to rectifying circuit 710.Accordingly, the rectified signal produced or output by rectifyingcircuit 710 is a half-wave rectified signal.

FIG. 15C is a schematic diagram of a rectifying circuit according to anexemplary embodiment. Referring to FIG. 15C, rectifying circuit 810includes a rectifying unit 815 and a terminal adapter circuit 541. Inthis embodiment, rectifying unit 815 comprises a half-wave rectifiercircuit including diodes 811 and 812 and configured to half-waverectify. Diode 811 has an anode connected to an output terminal 512, anda cathode connected to a half-wave node 819. Diode 812 has an anodeconnected to half-wave node 819, and a cathode connected to an outputterminal 511. Terminal adapter circuit 541 is coupled to half-wave node819 and pins 501 and 502, to transmit a signal received at pin 501and/or pin 502 to half-wave node 819. By means of the terminal adaptingfunction of terminal adapter circuit 541, rectifying circuit 810includes two input terminals (connected to pins 501 and 502) and twooutput terminals 511 and 512.

Next, in certain embodiments, rectifying circuit 810 operates asfollows.

During a received AC signal's positive half cycle, the AC signal may beinput through pin 501 or 502, terminal adapter circuit 541, half-wavenode 819, diode 812, and output terminal 511 in sequence, and lateroutput through another end or circuit of the LED tube lamp. During areceived AC signal's negative half cycle, the AC signal may be inputthrough another end or circuit of the LED tube lamp, and later outputthrough output terminal 512, diode 811, half-wave node 819, terminaladapter circuit 541, and pin 501 or 502 in sequence.

Terminal adapter circuit 541 may comprise a resistor, a capacitor, aninductor, or any combination thereof, for performing functions ofvoltage/current regulation or limiting, types of protection,current/voltage regulation, etc. Descriptions of these functions arepresented below.

In practice, rectifying unit 815 and terminal adapter circuit 541 may beinterchanged in position (as shown in FIG. 15D), without altering thefunction of half-wave rectification. FIG. 15D is a schematic diagram ofa rectifying circuit according to an embodiment. Referring to FIG. 15D,diode 811 has an anode connected to pin 502 and diode 812 has a cathodeconnected to pin 501. A cathode of diode 811 and an anode of diode 812are connected to half-wave node 819. Terminal adapter circuit 541 iscoupled to half-wave node 819 and output terminals 511 and 512. During areceived AC signal's positive half cycle, the AC signal may be inputthrough another end or circuit of the LED tube lamp, and later outputthrough output terminal 511 or 512, terminal adapter circuit 541,half-wave node 819, diode 812, and pin 501 in sequence. During areceived AC signal's negative half cycle, the AC signal may be inputthrough pin 502, diode 811, half-wave node 819, terminal adapter circuit541, and output node 511 or 512 in sequence, and later output throughanother end or circuit of the LED tube lamp.

Terminal adapter circuit 541 in embodiments shown in FIGS. 15C and 15Dmay be omitted and is therefore depicted by a dotted line. If terminaladapter circuit 541 of FIG. 15C is omitted, pins 501 and 502 will becoupled to half-wave node 819. If terminal adapter circuit 541 of FIG.15D is omitted, output terminals 511 and 512 will be coupled tohalf-wave node 819.

Rectifying circuit 510 as shown and explained in FIGS. 15A-D canconstitute or be the rectifying circuit 540 shown in FIG. 14E, as havingpins 503 and 504 for conducting instead of pins 501 and 502.

Next, an explanation follows as to choosing embodiments and theircombinations of rectifying circuits 510 and 540, with reference to FIGS.14C and 14E.

Rectifying circuit 510 in embodiments shown in FIG. 14C may comprise,for example, the rectifying circuit 610 in FIG. 15A.

Rectifying circuits 510 and 540 in embodiments shown in FIG. 14E mayeach comprise, for example, any one of the rectifying circuits in FIGS.15A-D, and terminal adapter circuit 541 in FIGS. 15C-D may be omittedwithout altering the rectification function used in an LED tube lamp.When rectifying circuits 510 and 540 each comprise a half-wave rectifiercircuit described in FIGS. 15B-D, during a received AC signal's positiveor negative half cycle, the AC signal may be input from one ofrectifying circuits 510 and 540, and later output from the otherrectifying circuit 510 or 540. Further, when rectifying circuits 510 and540 each comprise the rectifying circuit described in FIG. 15C or 15D,or when they comprise the rectifying circuits in FIGS. 15C and 15Drespectively, only one terminal adapter circuit 541 may be needed forfunctions of voltage/current regulation or limiting, types ofprotection, current/voltage regulation, etc. within rectifying circuits510 and 540, omitting another terminal adapter circuit 541 withinrectifying circuit 510 or 540.

FIG. 16A is a schematic diagram of a terminal adapter circuit accordingto an exemplary embodiment. Referring to FIG. 16A, terminal adaptercircuit 641 comprises a capacitor 642 having an end connected to pins501 and 502, and another end connected to half-wave node 819. In oneembodiment, capacitor 642 has an equivalent impedance to an AC signal,which impedance increases as the frequency of the AC signal decreases,and decreases as the frequency increases. Therefore, capacitor 642 interminal adapter circuit 641 in this embodiment works as a high-passfilter. Further, terminal adapter circuit 641 is connected in series toan LED unit in the LED tube lamp, producing an equivalent impedance ofterminal adapter circuit 641 to perform a current/voltage limitingfunction on the LED unit, thereby preventing damaging of the LED unit byan excessive voltage across and/or current in the LED unit. In addition,choosing the value of capacitor 642 according to the frequency of the ACsignal can further enhance voltage/current regulation.

Terminal adapter circuit 641 may further include a capacitor 645 and/orcapacitor 646. Capacitor 645 has an end connected to half-wave node 819,and another end connected to pin 503. Capacitor 646 has an end connectedto half-wave node 819, and another end connected to pin 504. Forexample, half-wave node 819 may be a common connective node betweencapacitors 645 and 646. And capacitor 642 acting as a current regulatingcapacitor is coupled to the common connective node and pins 501 and 502.In such a structure, series-connected capacitors 642 and 645 existbetween one of pins 501 and 502 and pin 503, and/or series-connectedcapacitors 642 and 646 exist between one of pins 501 and 502 and pin504. Through equivalent impedances of series-connected capacitors,voltages from the AC signal are divided. Referring to FIGS. 14E and 16A,according to ratios between equivalent impedances of theseries-connected capacitors, the voltages respectively across capacitor642 in rectifying circuit 510, filtering circuit 520, and LED lightingmodule 530 can be controlled, making the current flowing through an LEDmodule coupled to LED lighting module 530 being limited within a currentrating, and then protecting/preventing filtering circuit 520 and LEDmodule from being damaged by excessive voltages.

FIG. 16B is a schematic diagram of a terminal adapter circuit accordingto an exemplary embodiment. Referring to FIG. 16B, terminal adaptercircuit 741 comprises capacitors 743 and 744. Capacitor 743 has an endconnected to pin 501, and another end connected to half-wave node 819.Capacitor 744 has an end connected to pin 502, and another end connectedto half-wave node 819. Compared to terminal adapter circuit 641 in FIG.16A, terminal adapter circuit 741 has capacitors 743 and 744 in place ofcapacitor 642. Capacitance values of capacitors 743 and 744 may be thesame as each other, or may differ from each other depending on themagnitudes of signals to be received at pins 501 and 502.

Similarly, terminal adapter circuit 741 may further comprise a capacitor745 and/or a capacitor 746, respectively connected to pins 503 and 504.Thus, each of pins 501 and 502 and each of pins 503 and 504 may beconnected in series to a capacitor, to achieve the functions of voltagedivision and other protections.

FIG. 16C is a schematic diagram of the terminal adapter circuitaccording to an exemplary embodiment. Referring to FIG. 16C, terminaladapter circuit 841 comprises capacitors 842, 843, and 844. Capacitors842 and 843 are connected in series between pin 501 and half-wave node819. Capacitors 842 and 844 are connected in series between pin 502 andhalf-wave node 819. In such a circuit structure, if any one ofcapacitors 842, 843, and 844 is shorted, there is still at least onecapacitor (of the other two capacitors) between pin 501 and half-wavenode 819 and between pin 502 and half-wave node 819, which performs acurrent-limiting function. Therefore, in the event that a useraccidentally gets an electric shock, this circuit structure will preventan excessive current flowing through and then seriously hurting the bodyof the user.

Similarly, terminal adapter circuit 841 may further comprise a capacitor845 and/or a capacitor 846, respectively connected to pins 503 and 504.Thus, each of pins 501 and 502 and each of pins 503 and 504 may beconnected in series to a capacitor, to achieve the functions of voltagedivision and other protections.

FIG. 16D is a schematic diagram of a terminal adapter circuit accordingto an exemplary embodiment. Referring to FIG. 16D, terminal adaptercircuit 941 comprises fuses 947 and 948. Fuse 947 has an end connectedto pin 501, and another end connected to half-wave node 819. Fuse 948has an end connected to pin 502, and another end connected to half-wavenode 819. With the fuses 947 and 948, when the current through each ofpins 501 and 502 exceeds a current rating of a corresponding connectedfuse 947 or 948, the corresponding fuse 947 or 948 will accordingly meltand then break the circuit to achieve overcurrent protection. Theterminal adapter circuits described above may be described as currentlimiting circuits, and/or voltage limiting circuits.

Each of the embodiments of the terminal adapter circuits as described inrectifying circuits 510 and 810 coupled to pins 501 and 502 and shownand explained above can be used or included in the rectifying circuit540 shown in FIG. 14E, to be connected to conductive pins 503 and 504 ina similar manner as described above in connection with conductive pins501 and 502.

Capacitance values of the capacitors in the embodiments of the terminaladapter circuits shown and described above are in some embodiments inthe range, for example, of about 100 pF-100 nF. Also, a capacitor usedin embodiments may be equivalently replaced by two or more capacitorsconnected in series or parallel. For example, each of capacitors 642 and842 may be replaced by two series-connected capacitors, one having acapacitance value chosen from the range, for example of about 1.0 nF toabout 2.5 nF and which may be in some embodiments preferably 1.5 nF, andthe other having a capacitance value chosen from the range, for exampleof about 1.5 nF to about 3.0 nF, and which is in some embodiments about2.2 nF.

FIG. 17A is a block diagram of a filtering circuit according to anexemplary embodiment. Rectifying circuit 510 is shown in FIG. 17A forillustrating its connection with other components, without intendingfiltering circuit 520 to include rectifying circuit 510. Referring toFIG. 17A, filtering circuit 520 includes a filtering unit 523 coupled torectifying output terminals 511 and 512 to receive, and to filter outripples of a rectified signal from rectifying circuit 510, therebyoutputting a filtered signal whose waveform is smoother than therectified signal. Filtering circuit 520 may further comprise anotherfiltering unit 524 coupled between a rectifying circuit and a pin, whichare for example rectifying circuit 510 and pin 501, rectifying circuit510 and pin 502, rectifying circuit 540 and pin 503, or rectifyingcircuit 540 and pin 504. Filtering unit 524 is for filtering of aspecific frequency, in order to filter out a specific frequencycomponent of an external driving signal. In this embodiment of FIG. 17A,filtering unit 524 is coupled between rectifying circuit 510 and pin501. Filtering circuit 520 may further comprise another filtering unit525 coupled between one of pins 501 and 502 and a diode of rectifyingcircuit 510, or between one of pins 503 and 504 and a diode ofrectifying circuit 540, for reducing or filtering out electromagneticinterference (EMI). In this embodiment, filtering unit 525 is coupledbetween pin 501 and a diode (not shown in FIG. 17A) of rectifyingcircuit 510.

Since filtering units 524 and 525 may be present or omitted depending onactual circumstances of their uses, they are depicted by a dotted linein FIG. 17A. Filtering units 523, 524, and 525 may be referred to hereinas filtering sub-circuits of filtering circuit 520, or may be generallyreferred to as a filtering circuit.

FIG. 17B is a schematic diagram of a filtering unit according to anexemplary embodiment. Referring to FIG. 17B, filtering unit 623 includesa capacitor 625 having an end coupled to output terminal 511 and afiltering output terminal 521 and another end coupled to output terminal512 and a filtering output terminal 522, and is configured to low-passfilter a rectified signal from output terminals 511 and 512, so as tofilter out high-frequency components of the rectified signal and therebyoutput a filtered signal at output terminals 521 and 522.

FIG. 17C is a schematic diagram of a filtering unit according to anexemplary embodiment. Referring to FIG. 17C, filtering unit 723comprises a pi filter circuit including a capacitor 725, an inductor726, and a capacitor 727. As is well known, a pi filter circuit lookslike the symbol 7 in its shape or structure. Capacitor 725 has an endconnected to output terminal 511 and coupled to output terminal 521through inductor 726, and has another end connected to output terminals512 and 522. Inductor 726 is coupled between output terminals 511 and521. Capacitor 727 has an end connected to output terminal 521 andcoupled to output terminal 511 through inductor 726, and has another endconnected to output terminals 512 and 522.

As seen between output terminals 511 and 512 and output terminals 521and 522, filtering unit 723 compared to filtering unit 623 in FIG. 17Badditionally has inductor 726 and capacitor 727, which are likecapacitor 725 in performing low-pass filtering. Therefore, filteringunit 723 in this embodiment compared to filtering unit 623 in FIG. 17Bhas a better ability to filter out high-frequency components to output afiltered signal with a smoother waveform.

Inductance values of inductor 726 in the embodiment described above arechosen in some embodiments in the range of about 10 nH to about 10 mH.And capacitance values of capacitors 625, 725, and 727 in theembodiments described above are chosen in some embodiments in the range,for example, of about 100 pF to about 1 uF.

FIG. 17D is a schematic diagram of a filtering unit according to anexemplary embodiment. Referring to FIG. 17D, filtering unit 824 includesa capacitor 825 and an inductor 828 connected in parallel. Capacitor 825has an end coupled to pin 501, and another end coupled to rectifyingoutput terminal 511 (not shown), and is configured to high-pass filteran external driving signal input at pin 501, so as to filter outlow-frequency components of the external driving signal. Inductor 828has an end coupled to pin 501 and another end coupled to rectifyingoutput terminal 511, and is configured to low-pass filter an externaldriving signal input at pin 501, so as to filter out high-frequencycomponents of the external driving signal. Therefore, the combination ofcapacitor 825 and inductor 828 works to present high impedance to anexternal driving signal at one or more specific frequencies. Thus, theparallel-connected capacitor and inductor work to present a peakequivalent impedance to the external driving signal at a specificfrequency.

Through appropriately choosing a capacitance value of capacitor 825 andan inductance value of inductor 828, a center frequency ƒ on thehigh-impedance band may be set at a specific value given by

${f = \frac{1}{\left. {2\pi} \right)\overset{\_}{LC}}},$

where L denotes inductance of inductor 828 and C denotes capacitance ofcapacitor 825. The center frequency is in some embodiments in the rangeof about 20˜30 kHz, and may be in some embodiments about 25 kHz. In oneembodiment, an LED lamp with filtering unit 824 is able to be certifiedunder safety standards, for a specific center frequency, as provided byUnderwriters Laboratories (UL).

In some embodiments, filtering unit 824 may further comprise a resistor829, coupled between pin 501 and filtering output terminal 511. In FIG.17D, resistor 829 is connected in series to the parallel-connectedcapacitor 825 and inductor 828. For example, resistor 829 may be coupledbetween pin 501 and parallel-connected capacitor 825 and inductor 828,or may be coupled between filtering output terminal 511 andparallel-connected capacitor 825 and inductor 828. In this embodiment,resistor 829 is coupled between pin 501 and parallel-connected capacitor825 and inductor 828. Further, resistor 829 is configured for adjustingthe quality factor (Q) of the LC circuit comprising capacitor 825 andinductor 828, to better adapt filtering unit 824 to applicationenvironments with different quality factor requirements. Since resistor829 is an optional component, it is depicted in a dotted line in FIG.17D.

Capacitance values of capacitor 825 are in some embodiments in the rangeof about 10 nF-2 uF. Inductance values of inductor 828 are in someembodiments smaller than 2 mH, and may be in some embodiments smallerthan 1 mH. Resistance value of resistor 829 are in some embodimentslarger than 50 ohms, and may be in some embodiments larger than 500ohms.

Besides the filtering circuits shown and described in the aboveembodiments, traditional low-pass or band-pass filters can be used asthe filtering unit in the filtering circuit in the present invention.

FIG. 17E is a schematic diagram of a filtering unit according to anexemplary embodiment. Referring to FIG. 17E, in this embodimentfiltering unit 925 is disposed in rectifying circuit 610 as shown inFIG. 15A, and is configured for reducing the EMI (Electromagneticinterference) caused by rectifying circuit 610 and/or other circuits. Inthis embodiment, filtering unit 925 includes an EMI-reducing capacitorcoupled between pin 501 and the anode of rectifying diode 613, and alsobetween pin 502 and the anode of rectifying diode 614, to reduce the EMIassociated with the positive half cycle of the AC driving signalreceived at pins 501 and 502. The EMI-reducing capacitor of filteringunit 925 is also coupled between pin 501 and the cathode of rectifyingdiode 611, and between pin 502 and the cathode of rectifying diode 612,to reduce the EMI associated with the negative half cycle of the ACdriving signal received at pins 501 and 502. In some embodiments,rectifying circuit 610 comprises a full-wave bridge rectifier circuitincluding four rectifying diodes 611, 612, 613, and 614. The full-wavebridge rectifier circuit has a first filtering node connecting an anodeand a cathode respectively of two diodes 613 and 611 of the fourrectifying diodes 611, 612, 613, and 614, and a second filtering nodeconnecting an anode and a cathode respectively of the other two diodes614 and 612 of the four rectifying diodes 611, 612, 613, and 614. Andthe EMI-reducing capacitor of the filtering unit 925 is coupled betweenthe first filtering node and the second filtering node.

Similarly, with reference to FIGS. 15C, and 16A-16C, each capacitor ineach of the circuits in FIGS. 16A-16C may be coupled between pins 501and 502 (or pins 503 and 504) and any diode in FIG. 15C, so any or eachcapacitor in FIGS. 16A-16C can work as an EMI-reducing capacitor toachieve the function of reducing EMI. For example, rectifying circuit510 in FIGS. 14C and 14E may comprise a half-wave rectifier circuitincluding two rectifying diodes and having a half-wave node connectingan anode and a cathode respectively of the two rectifying diodes, andany or each capacitor in FIGS. 16A-16C may be coupled between thehalf-wave node and at least one of the first pin and the second pin. Andrectifying circuit 540 in FIG. 14E may comprise a half-wave rectifiercircuit including two rectifying diodes and having a half-wave nodeconnecting an anode and a cathode respectively of the two rectifyingdiodes, and any or each capacitor in FIGS. 16A-16C may be coupledbetween the half-wave node and at least one of the third pin and thefourth pin.

It's worth noting that the EMI-reducing capacitor in the embodiment ofFIG. 17E may also act as capacitor 825 in filtering unit 824, so that incombination with inductor 828 the capacitor 825 performs the functionsof reducing EMI and presenting high impedance to an external drivingsignal at specific frequencies. For example, when the rectifying circuitcomprises a full-wave bridge rectifier circuit, capacitor 825 offiltering unit 824 may be coupled between the first filtering node andthe second filtering node of the full-wave bridge rectifier circuit.When the rectifying circuit comprises a half-wave rectifier circuit,capacitor 825 of filtering unit 824 may be coupled between the half-wavenode of the half-wave rectifier circuit and at least one of the firstpin and the second pin.

FIG. 18A is a schematic diagram of an LED module according to anexemplary embodiment. Referring to FIG. 18A, LED module 630 has an anodeconnected to the filtering output terminal 521, has a cathode connectedto the filtering output terminal 522, and comprises at least one LEDunit 632. When two or more LED units are included, they are connected inparallel. An anode of each LED unit 632 forms the anode of LED module630 and is connected to output terminal 521, and a cathode of each LEDunit 632 forms the cathode of LED module 630 and is connected to outputterminal 522. Each LED unit 632 includes at least one LED 631. Whenmultiple LEDs 631 are included in an LED unit 632, they are connected inseries, with the anode of the first LED 631 forming the anode of the LEDunit 632 that it is a part of, and the cathode of the first LED 631connected to the next or second LED 631. And the anode of the last LED631 in this LED unit 632 is connected to the cathode of a previous LED631, with the cathode of the last LED 631 forming the cathode of the LEDunit 632 that it is a part of.

In some embodiments, the LED module 630 may produce a current detectionsignal S531 reflecting a magnitude of current through LED module 630 andused for controlling or detecting current on the LED module 630. Asdescribed herein, an LED unit may refer to a single string of LEDsarranged in series, and an LED module may refer to a single LED unit, ora plurality of LED units connected to a same two nodes (e.g., arrangedin parallel). For example, the LED light strip 2 described above may bean LED module and/or LED unit.

FIG. 18B is a schematic diagram of an LED module according to anexemplary embodiment. Referring to FIG. 18B, LED module 630 has an anodeconnected to the filtering output terminal 521, has a cathode connectedto the filtering output terminal 522, and comprises at least two LEDunits 732, with an anode of each LED unit 732 forming the anode of LEDmodule 630, and a cathode of each LED unit 732 forming the cathode ofLED module 630. Each LED unit 732 includes at least two LEDs 731connected in the same way as described in FIG. 18A. For example, theanode of the first LED 731 in an LED unit 732 forms the anode of the LEDunit 732 that it is a part of, the cathode of the first LED 731 isconnected to the anode of the next or second LED 731, and the cathode ofthe last LED 731 forms the cathode of the LED unit 732 that it is a partof. Further, LED units 732 in an LED module 630 are connected to eachother in this embodiment. All of the n-th LEDs 731 respectively of theLED units 732 are connected by every anode of every n-th LED 731 in theLED units 732, and by every cathode of every n-th LED 731, where n is apositive integer. In this way, the LEDs in LED module 630 in thisembodiment are connected in the form of a mesh.

In some embodiments, LED lighting module 530 of the above embodimentsincludes LED module 630, but doesn't include a driving circuit for theLED module 630 (e.g., does not include an LED driving unit for the LEDmodule or LED unit).

Similarly, LED module 630 in this embodiment may produce a currentdetection signal S531 reflecting a magnitude of current through LEDmodule 630 and used for controlling or detecting current on the LEDmodule 630.

In actual practice, the number of LEDs 731 included by an LED unit 732is in some embodiments in the range of 15-25, and is may be preferablyin the range of 18-22.

In various embodiments, an exemplary LED tube lamp may have at leastsome of the electronic components of its power supply module disposed onan LED light strip of the LED tube lamp. For example, the technique ofprinted electronic circuit (PEC) can be used to print, insert, or embedat least some of the electronic components onto the LED light strip(e.g., as opposed to being on a separate circuit board connected to theLED light strip).

In one embodiment, all electronic components of the power supply moduleare disposed directly on the LED light strip. For example, theproduction process may include or proceed with the following steps:preparation of the circuit substrate (e.g. preparation of a flexibleprinted circuit board); ink jet printing of metallic nano-ink; ink jetprinting of active and passive components (as of the power supplymodule); drying/sintering; ink jet printing of interlayer bumps;spraying of insulating ink; ink jet printing of metallic nano-ink; inkjet printing of active and passive components (to sequentially form theincluded layers); spraying of surface bond pad(s); and spraying ofsolder resist against LED components. The production process may bedifferent, however, and still result in some or all electroniccomponents of the power supply module being disposed directly on the LEDlight strip.

In certain embodiments, if all electronic components of the power supplymodule are disposed on the light strip, electrical connection betweenterminal pins of the LED tube lamp and the light strip may be achievedby connecting the pins to conductive lines which are welded with ends ofthe light strip. In this case, another substrate for supporting thepower supply module is not required, thereby allowing of an improveddesign or arrangement in the end cap(s) of the LED tube lamp. In someembodiments, (components of) the power supply module are disposed at twoends of the light strip, in order to significantly reduce the impact ofheat generated from the power supply module's operations on the LEDcomponents. Since no substrate other than the light strip is used tosupport the power supply module in this case, the total amount ofwelding or soldering can be significantly reduced, improving the generalreliability of the power supply module. If no additional substrate isused, the electronic components of the power supply module disposed onthe light strip may still be positioned in the end cap(s) of the LEDtube lamp, or they may be positioned partly or wholly inside the lamptube but not in the end cap(s).

Another case is that some of all electronic components of the powersupply module, such as some resistors and/or smaller size capacitors,are printed onto the light strip, and some bigger size components, suchas some inductors and/or electrolytic capacitors, are disposed onanother substrate, for example in the end cap(s). The production processof the light strip in this case may be the same as that described above.And in this case disposing some of all electronic components on thelight strip is conducive to achieving a reasonable layout of the powersupply module in the LED tube lamp, which may allow of an improveddesign in the end cap(s).

As a variant embodiment of the above, electronic components of the powersupply module may be disposed on the light strip by a method ofembedding or inserting, e.g. by embedding the components onto a bendableor flexible light strip. In some embodiments, this embedding may berealized by a method using copper-clad laminates (CCL) for forming aresistor or capacitor; a method using ink related to silkscreenprinting; or a method of ink jet printing to embed passive components,wherein an ink jet printer is used to directly print inks to constitutepassive components and related functionalities to intended positions onthe light strip. Then through treatment by ultraviolet (UV) light ordrying/sintering, the light strip is formed where passive components areembedded. The electronic components embedded onto the light stripinclude for example resistors, capacitors, and inductors. In otherembodiments, active components also may be embedded. Through embeddingsome components onto the light strip, a reasonable layout of the powersupply module can be achieved to allow of an improved design in the endcap(s), because the surface area on a printed circuit board used forcarrying components of the power supply module is reduced or smaller,and as a result the size, weight, and thickness of the resulting printedcircuit board for carrying components of the power supply module is alsosmaller or reduced. Also in this situation since welding points on theprinted circuit board for welding resistors and/or capacitors if theywere not to be disposed on the light strip are no longer used, thereliability of the power supply module is improved, in view of the factthat these welding points are very liable to (cause or incur) faults,malfunctions, or failures. Further, the length of conductive linesneeded for connecting components on the printed circuit board istherefore also reduced, which allows of a more compact layout ofcomponents on the printed circuit board and thus improving thefunctionalities of these components.

In some embodiments, luminous efficacy of the LED or LED component is 80lm/W or above, and in some embodiments, it may be preferably 120 lm/W orabove. Certain more optimal embodiments may include a luminous efficacyof the LED or LED component of 160 lm/W or above. White light emitted byan LED component may be produced by mixing fluorescent powder with themono chromatic light emitted by a monochromatic LED chip. The whitelight in its spectrum has major wavelength ranges of 430-460 nm and550-560 nm, or major wavelength ranges of 430-460 nm, 540-560 nm, and620-640 nm.

FIG. 18C is an exemplary plan view of a circuit layout of an LED moduleaccording to certain embodiments. Referring to FIG. 18C, in thisembodiment LEDs 831 are connected in the same way as described in FIG.18B, and three LED units are assumed in LED module 630 and described asfollows for illustration. A positive conductive line 834 and a negativeconductive line 835 are to receive a driving signal, for supplying powerto the LEDs 831. For example, positive conductive line 834 may becoupled to the filtering output terminal 521 of the filtering circuit520 described above, and negative conductive line 835 coupled to thefiltering output terminal 522 of the filtering circuit 520, to receive afiltered signal. For the convenience of illustration, all three of then-th LEDs 831 respectively of the three LED units are grouped as an LEDset 833 in FIG. 18C.

Positive conductive line 834 connects the three first LEDs 831respectively of the three LED units, at the anodes on the left sides ofthe three first LEDs 831 as shown in the leftmost LED set 833 of FIG.18C. The three first LEDs 831 may be the leftmost LEDs for each LED unitrespectively. Negative conductive line 835 connects the three last LEDs831 respectively of the three LED units, at the cathodes on the rightsides of the three last LEDs 831 as shown in the rightmost LED set 833of FIG. 18C. The three last LEDs 831 may be the rightmost LEDs for eachLED unit respectively. For the three LED units, the cathodes of thethree first LEDs 831, the anodes of the three last LEDs 831, and theanodes and cathodes of all the remaining LEDs 831 are connected byconductive lines or parts 839, also referred to as internal conductiveconnectors.

For example, the anodes of the three LEDs 831 in the leftmost LED set833 may be connected together by positive conductive line 834, and theircathodes may be connected together by a leftmost conductive part 839.The anodes of the three LEDs 831 in the second leftmost LED set 833 arealso connected together by the leftmost conductive part 839, whereastheir cathodes are connected together by a second, next-leftmostconductive part 839. Since the cathodes of the three LEDs 831 in theleftmost LED set 833 and the anodes of the three LEDs 831 in the second,next-leftmost LED set 833 are connected together by the same leftmostconductive part 839, in each of the three LED units the cathode of thefirst LED 831 is connected to the anode of the next or second LED 831,with the remaining LEDs 831 also being connected in the same way.Accordingly, all the LEDs 831 of the three LED units are connected toform the mesh as shown in FIG. 18B. The LED module shown in FIG. 18C mayform an LED light strip 2 such as described above.

It's worth noting that in the embodiment shown in FIG. 18C, the length836 (e.g., length along a first direction that is a length direction ofthe LED light strip 2 and lamp tube 1) of a portion of each conductivepart 839 that immediately connects to the anode of an LED 831 is smallerthan the length 837 of another portion of each conductive part 839 thatimmediately connects to the cathode of an LED 831, making the area ofthe latter portion immediately connecting to the cathode larger thanthat of the former portion immediately connecting to the anode. Thelength 837 may be smaller than a length 838 of a portion of eachconductive part 839 that immediately connects the cathode of an LED 831and the anode of the next LED 831, making the area of the portion ofeach conductive part 839 that immediately connects a cathode and ananode larger than the area of any other portion of each conductive part839 that immediately connects to only a cathode or an anode of an LED831. Due to the length differences and area differences, this layoutstructure improves heat dissipation of the LEDs 831.

In some embodiments, positive conductive line 834 includes a lengthwiseportion 834 a, and negative conductive line 835 includes a lengthwiseportion 835 a, which are conducive to making the LED module have apositive “+” connective portion and a negative “−” connective portion ateach of the two ends of the LED module, as shown in FIG. 18C. Such alayout structure allows for coupling certain of the various circuits ofthe power supply module of the LED lamp, including e.g. filteringcircuit 520 and rectifying circuits 510 and 540, to the LED modulethrough the positive connective portion and/or the negative connectiveportion at each or both ends of the LED lamp. Thus the layout structureincreases the flexibility in arranging actual circuits in the LED lamp.

As shown in FIG. 18C, positive conductive line 834, negative conductiveline 835, and conductive lines or parts 839 in a conductive layer of thelight strip 2 are laid out in orthogonal shapes or composed oforthogonal parts (e.g., having 90 degree angles) with LEDs 831, sofinished products of the light strip 2 in their portions of suchcircuit/wiring layout may be prone to curve or be deformed, whichcurving may cause abnormalities of mounted chip devices described abovewith reference to FIGS. 5B-5G, adversely affect lighting efficiencies ofthe LEDs in operation and the process of assembling the light strip 2 inan LED tube lamp, especially when mounting of LEDs 831 as in chip formis significantly adopted on the light strip 2. In view of thesedisadvantages, an improved way to lay out circuit or wiring in theconductive layer of the light strip 2 is illustrated in FIG. 18D.

FIG. 18D is a plan view of an improved circuit layout method in an LEDmodule applicable to some embodiments. Compared to the layout structurein FIG. 18C, when mounting of LEDs 1231 as in chip form is to besignificantly adopted on the light strip 2, conductive lines or parts1239 in a conductive layer of the light strip 2 in FIG. 18D are laid outwith oblique edges, or composed of oblique corresponding edges, whichedges may be used to bear, or are adjacent to portions of conductivelines or parts 1239 which bear, bonding pads to which LEDs 1231 are tobe mounted. Such laying out with oblique edges of conductive lines orparts 1239 can make the overall strength of the material of theconductive layer, such as copper, more even or uniform, and thus make iteasier for the LEDs 1231 to be mounted/attached to conductive lines orparts 1239, resulting in better reliability of assembling the lightstrip 2 in an LED tube lamp.

Benefits of using the improved circuit layout method in making the lightstrip 2 may include one or more of: more balanced release of stress fromthe light strip 2; such light strip 2 is less likely to curve or bedeformed; reduced incidence of abnormalities in the conductive layersuch as undesired open-circuit and poor electrical/physical contact;and/or better overall reliability of the light strip 2. And the improvedcircuit layout method is applicable in making a light strip 2 in both anLED tube lamp to be supplied by an electrical ballast as a power source,and an LED tube lamp to be supplied by an AC power source instead of aballast. In addition, as to arrangement of different electrical devicesto be laid out on the light strip 2, in various embodiments LEDs831/1231 and filtering capacitor(s) 625 would be disposed on or close toa center portion of the light strip 2, and resistor(s) and othercapacitor(s) would preferably be disposed close to but not on terminalor end regions of the light strip 2.

FIG. 19 is a block diagram showing components of an LED lamp (e.g., anLED tube lamp) according to an exemplary embodiment. As shown in FIG.19, the power supply module of the LED lamp includes rectifying circuits510 and 540, a filtering circuit 520, and an LED driving circuit 1530,wherein an LED lighting module 530 includes the driving circuit 1530 andan LED module 630. According to the above description in FIG. 14E,driving circuit 1530 in FIG. 19 comprises a DC-to-DC converter circuit,and is coupled to filtering output terminals 521 and 522 to receive afiltered signal and then perform power conversion for converting thefiltered signal into a driving signal at driving output terminals 1521and 1522. The LED module 630 is coupled to driving output terminals 1521and 1522 to receive the driving signal for emitting light. In someembodiments, the current of LED module 630 is stabilized at an objectivecurrent value. Exemplary descriptions of this LED module 630 are thesame as those provided above with reference to FIGS. 18A-18B.

In some embodiments, the rectifying circuit 540 is an optional elementand therefore can be omitted, so it is depicted in a dotted line in FIG.19. Therefore, the power supply module of the LED lamp in thisembodiment can be used with a single-end power supply coupled to one endof the LED lamp, and can be used with a dual-end power supply coupled totwo ends of the LED lamp. With a single-end power supply, examples ofthe LED lamp include an LED light bulb, a personal area light (PAL),etc.

With reference back to FIGS. 7 and 8, a short circuit board 253 includesa first short circuit substrate and a second short circuit substraterespectively connected to two terminal portions of a long circuit sheet251, and electronic components of the power supply module arerespectively disposed on the first short circuit substrate and thesecond short circuit substrate. The first short circuit substrate may bereferred to as a first power supply substrate, or first end capsubstrate. The second short circuit substrate may be referred to as asecond power supply substrate, or second end cap substrate. The firstpower supply substrate and second power supply substrate may be separatesubstrates at different ends of an LED tube lamp.

The first short circuit substrate and the second short circuit substratemay have roughly the same length, or different lengths. In someembodiments, a first short circuit substrate (e.g. the right circuitsubstrate of short circuit board 253 in FIG. 7 and the left circuitsubstrate of short circuit board 253 in FIG. 8) has a length that isabout 30%-80% of the length of the second short circuit substrate (i.e.the left circuit substrate of short circuit board 253 in FIG. 7 and theright circuit substrate of short circuit board 253 in FIG. 8). In someembodiments the length of the first short circuit substrate is about ⅓˜⅔ of the length of the second short circuit substrate. For example, inone embodiment, the length of the first short circuit substrate may beabout half the length of the second short circuit substrate. The lengthof the second short circuit substrate may be, for example in the rangeof about 15 mm to about 65 mm, depending on actual applicationoccasions. In certain embodiments, the first short circuit substrate isdisposed in an end cap at an end of the LED tube lamp, and the secondshort circuit substrate is disposed in another end cap at the oppositeend of the LED tube lamp.

Some or all capacitors of the driving circuit in the power supply modulemay be arranged on the first short circuit substrate of short circuitboard 253, while other components such as the rectifying circuit,filtering circuit, inductor(s) of the driving circuit, controller(s),switch(es), diodes, etc. are arranged on the second short circuitsubstrate of short circuit board 253. Since inductors, controllers,switches, etc. are electronic components with higher temperature,arranging some or all capacitors on a circuit substrate separate or awayfrom the circuit substrate(s) of high-temperature components helpsprevent the working life of capacitors (especially electrolyticcapacitors) from being negatively affected by the high-temperaturecomponents, thus improving the reliability of the capacitors. Further,the physical separation between the capacitors and both the rectifyingcircuit and filtering circuit also contributes to reducing the problemof EMI.

In some embodiments, the driving circuit has power conversion efficiencyof 80% or above, which may in some embodiments be 90% or above, and mayin some embodiments be 92% or above. Therefore, without the drivingcircuit, luminous efficacy of the LED lamp according to some embodimentsmay preferably be 120 lm/W or above, and may even more preferably be 160lm/W or above. On the other hand, with the driving circuit incombination with the LED component(s), luminous efficacy of the LED lampmay preferably be, in some embodiments, 120 lm/W*90%=108 lm/W or above,and may even more preferably be, in some embodiments 160 lm/W*92%=147.2lm/W or above.

In view of the fact that the diffusion film or layer in an LED tube lampgenerally has light transmittance of 85% or above, luminous efficacy ofthe LED tube lamp in some embodiments is 108 lm/W*85%=91.8 lm/W orabove, and may be, in some more effective embodiments, 147.2lm/W*85%125.12 lm/W.

FIG. 20A is a block diagram of an LED lamp according to an exemplaryembodiment. Compared to FIG. 19, the embodiment of FIG. 20A includesrectifying circuits 510 and 540, and a filtering circuit 520, andfurther includes an anti-flickering circuit 550; wherein the powersupply module may also include some components of an LED lighting module530. The anti-flickering circuit 550 is coupled between filteringcircuit 520 and LED lighting module 530. It's noted that rectifyingcircuit 540 may be omitted, as is depicted by the dotted line in FIG.20A.

Anti-flickering circuit 550 is coupled to filtering output terminals 521and 522, to receive a filtered signal, and under specific circumstancesto consume partial energy of the filtered signal so as to reduce (theincidence of) ripples of the filtered signal disrupting or interruptingthe light emission of the LED lighting module 530. In general, filteringcircuit 520 has such filtering components as resistor(s) and/orinductor(s), and/or parasitic capacitors and inductors, which may formresonant circuits. Upon breakoff or stop of an AC power signal, as whenthe power supply of the LED lamp is turned off by a user, theamplitude(s) of resonant signals in the resonant circuits will decreasewith time. But LEDs in the LED module of the LED lamp are unidirectionalconduction devices and require a minimum conduction voltage for the LEDmodule. When a resonant signal's trough value is lower than the minimumconduction voltage of the LED module, but its peak value is still higherthan the minimum conduction voltage, the flickering phenomenon willoccur in light emission of the LED module. In this case anti-flickeringcircuit 550 works by allowing a current matching a defined flickeringcurrent value of the LED component to flow through, consuming partialenergy of the filtered signal which should be higher than the energydifference of the resonant signal between its peak and trough values, soas to reduce the flickering phenomenon. In certain embodiments, theanti-flickering circuit 550 may operate when the filtered signal'svoltage approaches (and is still higher than) the minimum conductionvoltage.

In some embodiments, the anti-flickering circuit 550 may be moresuitable for the situation in which LED lighting module 530 doesn'tinclude driving circuit 1530, for example, when LED module 630 of LEDlighting module 530 is (directly) driven to emit light by a filteredsignal from a filtering circuit. In this case, the light emission of LEDmodule 630 will directly reflect variation in the filtered signal due toits ripples. In this situation, the introduction of anti-flickeringcircuit 550 will prevent the flickering phenomenon from occurring in theLED lamp upon the breakoff of power supply to the LED lamp.

FIG. 20B is a schematic diagram of the anti-flickering circuit accordingto an exemplary embodiment. Referring to FIG. 20B, anti-flickeringcircuit 650 includes at least a resistor, such as two resistorsconnected in series between filtering output terminals 521 and 522. Inthis embodiment, anti-flickering circuit 650 in use consumes partialenergy of a filtered signal continually. When in normal operation of theLED lamp, this partial energy is far lower than the energy consumed byLED lighting module 530. But upon a breakoff or stop of the powersupply, when the voltage level of the filtered signal decreases toapproach the minimum conduction voltage of LED module 630, this partialenergy is still consumed by anti-flickering circuit 650 in order tooffset the impact of the resonant signals which may cause the flickeringof light emission of LED module 630. In some embodiments, a currentequal to or larger than an anti-flickering current level may be set toflow through anti-flickering circuit 650 when LED module 630 is suppliedby the minimum conduction voltage, and then an equivalentanti-flickering resistance of anti-flickering circuit 650 can bedetermined based on the set current.

FIG. 21A is a block diagram of an LED lamp according to an exemplaryembodiment. Compared to FIG. 19, the embodiment of FIG. 21A includesrectifying circuits 510 and 540, a filtering circuit 520, and a drivingcircuit 1530, and further includes a mode switching circuit 580; whereinan LED lighting module 530 is composed of driving circuit 1530 and anLED module 630. Mode switching circuit 580 is coupled to at least one offiltering output terminals 521 and 522 and at least one of drivingoutput terminals 1521 and 1522, for determining whether to perform afirst driving mode or a second driving mode, as according to a frequencyof the external driving signal. In the first driving mode, a filteredsignal from filtering circuit 520 is input into driving circuit 1530,while in the second driving mode the filtered signal bypasses at least acomponent of driving circuit 1530, making driving circuit 1530 stopworking in conducting the filtered signal, allowing the filtered signalto (directly) reach and drive LED module 630. The bypassed component(s)of driving circuit 1530 may include an inductor or a switch, which whenbypassed makes driving circuit 1530 unable to transfer and/or convertpower, and then stop working in conducting the filtered signal. Ifdriving circuit 1530 includes a capacitor, the capacitor can still beused to filter out ripples of the filtered signal in order to stabilizethe voltage across the LED module. When mode switching circuit 580determines to perform the first driving mode, allowing the filteredsignal to be input to driving circuit 1530, driving circuit 1530 thentransforms the filtered signal into a driving signal for driving LEDmodule 630 to emit light. On the other hand, when mode switching circuit580 determines to perform the second driving mode, allowing the filteredsignal to bypass driving circuit 1530 to reach LED module 630, filteringcircuit 520 then becomes in effect a driving circuit for LED module 630.Then filtering circuit 520 provides the filtered signal as a drivingsignal for the LED module for driving the LED module to emit light.

In some embodiments, the mode switching circuit 580 can determinewhether to perform the first driving mode or the second driving modebased on a user's instruction or a detected signal received by the LEDlamp through pins 501, 502, 503, and 504. In some embodiments, a modedetermination circuit 590 is used to determine the first driving mode orthe second driving mode based on a signal received by the LED lamp andso the mode switching circuit 580 can determine whether to perform thefirst driving mode or the second driving mode based on a determinedresult signal S580 or/and S585. With the mode switching circuit, thepower supply module of the LED lamp can adapt to or perform one ofappropriate driving modes corresponding to different applicationenvironments or driving systems, thus improving the compatibility of theLED lamp. In some embodiments, rectifying circuit 540 may be omitted, asis depicted by the dotted line in FIG. 21A.

FIG. 21B is a schematic diagram of a mode determination circuit in anLED lamp according to an exemplary embodiment. Referring to FIG. 21B,the mode determination circuit 690 comprises a symmetrical trigger diode691 and a resistor 692, configured to detect a voltage level of anexternal driving signal. The symmetrical trigger diode 691 and theresistor 692 are connected in series; and namely, one end of thesymmetrical trigger diode 691 is coupled to the first filtering outputterminal 521, the other end thereof is coupled to one end of theresistor 692, and the other end of the resistor 692 is coupled to thesecond filtering output terminal 522. A connection node of thesymmetrical trigger diode 691 and the resistor 692 generates adetermined result signal S580 transmitted to a mode switching circuit.When an external driving signal is a signal with high frequency and highvoltage, the determined result signal S580 is at a high voltage level tomake the mode switching circuit determine to operate at the seconddriving mode. For example, when the lamp driving circuit 505, as shownin FIG. 14A and FIG. 14D, exists, the lamp driving circuit 505 convertsthe AC power signal of the AC power supply 508 into an AC driving signalwith high frequency and high voltage, transmitted into the LED tube lamp500. At this time, the mode switching circuit determines to operate atthe second driving mode and so the filtered signal, outputted by a firstfiltering output terminal 521 and a second filtering output terminal522, directly drive the LED module 630 to light. When the externaldriving signal is a signal with low frequency and low voltage, thedetermined result signal S580 is at a low voltage level to make the modeswitching circuit determine to operate at the first driving mode. Forexample, when the lamp driving circuit 505, as shown in FIG. 14A andFIG. 14D, does not exist, the AC power signal of the AC power supply 508is directly transmitted into the LED tube lamp 500. At this time, themode switching circuit determines to operate at the first driving modeand so the filtered signal, outputted by the first filtering outputterminal 521 and the second filtering output terminal 522, is convertedinto an appropriate voltage level to drive the LED module 630 to light.

In some embodiments, a break over voltage of the symmetrical triggerdiode 691 is in a range of 400V˜1300V, in some embodiments morespecifically in a range of 450V˜700V, and in some embodiments morespecifically in a range of 500V˜600V.

The mode determination circuit 690 may include a resistor 693 and aswitch 694. The resistor 693 and the switch 694 could be omitted basedon the practice application, thus the resistor 693 and the switch 694and a connection line thereof are depicted in a dotted line in FIG. 21B.The resistor 693 and the switch 694 are connected in series; namely oneend of the resistor 693 is coupled to the first filtering outputterminal 521, the other end is coupled to one end of the switch 694, andanother end of the switch 694 is coupled to a second filtering outputterminal 522. A control end of the switch 694 is coupled to theconnection node of the symmetrical trigger diode 691 and the resistor692 for receiving the determined result signal S580. Accordingly, aconnection node of the resistor 693 and the switch 694 generates anotherdetermined result signal S585. The determined result signal S585 is aninverted signal of the determined result signal S580 and so they couldbe applied to a mode switching circuit having switches for switchingbetween two modes.

FIG. 21C is a schematic diagram of a mode determination circuit in anLED lamp according to an exemplary embodiment. Referring to FIG. 21C,the mode determination circuit 790 includes a capacitor 791, resistors792 and 793, and a switch 794. The capacitor 791 and the resistor 792are connected in series as a frequency determination circuit 795 fordetecting a frequency of an external driving signal. One end of thecapacitor 792 is coupled to a first rectifying output terminal 511, theother end is coupled to one end of the resistor 791, and the other endof the resistor 791 is coupled to a second rectifying output terminal512. The frequency determination circuit 795 generates the determinedresult signal S580 at a connection node of the resistor 791 and thecapacitor 792. A voltage level of the determined result signal S580 isdetermined based on the frequency of the external driving signal. Insome embodiments, the higher the frequency of the external drivingsignal is, the higher the voltage level of the determined result signalS580 is, and the lower the frequency of the external driving signal is,the lower the voltage level of the determined result signal S580 is.Hence, when the external driving signal is a higher frequency signal(e.g., more than 20 KHz) and high voltage, the determined result signalS580 is at high voltage level to make the mode switching circuitdetermine to operate at second driving mode. When the external drivingsignal is a lower frequency signal and low voltage signal, thedetermined result signal S580 is at a low voltage level to make the modeswitching circuit determine to operate at first driving mode. Similarly,in some embodiments, the mode determination circuit 790 may include aresistor 793 and a switch 794. The resistor 793 and the switch 794 areconnected in series between the first filtering output terminal 521 andthe second filtering output terminal 522, and a control end of theswitch 794 is coupled to the frequency determination circuit 795 toreceive the determined result signal S580. Accordingly, anotherdetermined result signal S585 is generated at a connection node of theresistor 793 and the switch 794 and is an inverted signal of thedetermined result signal S580. The determined result signals S580 andS585 may be applied to a mode switching circuit having two switches. Theresistor 793 and the switch 794 could be omitted based on practiceapplication and so are depicted in a dotted line

FIG. 22A is a block diagram of an LED lamp according to an exemplaryembodiment. Compared to FIG. 14E, the embodiment of FIG. 22A includesrectifying circuits 510 and 540, and a filtering circuit 520, andfurther includes a ballast interface circuit 1510; wherein the powersupply module may also include some components of an LED lighting module530. The ballast interface circuit 1510 is coupled to (the first)rectifying circuit 510, and may be coupled between pin 501 and/or pin502 and rectifying circuit 510. This embodiment is explained assumingthe ballast interface circuit 1510 to be coupled between pin 501 andrectifying circuit 510. With reference to FIGS. 14A and 14D in additionto FIG. 22A, in one embodiment, lamp driving circuit 505 comprises aballast configured to provide an AC driving signal to drive the LEDlamp.

In an initial stage upon the activation of the driving system of lampdriving circuit 505, lamp driving circuit 505's ability to outputrelevant signal(s) initially takes time to rise to a standard state, andat first has not risen to that state. However, in the initial stage thepower supply module of the LED lamp instantly or rapidly receives orconducts the AC driving signal provided by lamp driving circuit 505,which initial conduction is likely to fail the starting of the LED lampby lamp driving circuit 505 as lamp driving circuit 505 is initiallyloaded by the LED lamp in this stage. For example, internal componentsof lamp driving circuit 505 may retrieve power from a transformed outputin lamp driving circuit 505, in order to maintain their operation uponthe activation. In this case, the activation of lamp driving circuit 505may end up failing as its output voltage could not normally rise to arequired level in this initial stage; or the quality factor (Q) of aresonant circuit in lamp driving circuit 505 may vary as a result of theinitial loading from the LED lamp, so as to cause the failure of theactivation.

In one embodiment, in the initial stage upon activation, ballastinterface circuit 1510 will be in an open-circuit state, preventing theenergy of the AC driving signal from reaching the LED module. After adefined delay, which may be a specific delay period, after the ACdriving signal as an external driving signal is first input to the LEDtube lamp, ballast interface circuit 1510 switches, or changes, from acutoff state during the delay to a conducting state, allowing the energyof the AC driving signal to start to reach the LED module. By means ofthe delayed conduction of ballast interface circuit 1510, operation ofthe LED lamp simulates the lamp-starting characteristics of afluorescent lamp. For example, during lamp starting of a fluorescentlamp, internal gases of the fluorescent lamp will normally discharge forlight emission after a delay upon activation of a driving power supply.Therefore, ballast interface circuit 1510 further improves thecompatibility of the LED lamp with lamp driving circuits 505 such as anelectronic ballast. In this manner, ballast interface circuit 1510,which may be described as a delay circuit, or an external signal controlcircuit, is configured to control and controls the timing for receivingan AC driving signal at a power supply module of an LED lamp (e.g., at arectifier circuit and/or filter circuit of a power supply module).

In this embodiment, rectifying circuit 540 may be omitted and istherefore depicted by a dotted line in FIG. 22A.

In the embodiments using the ballast interface circuit described withreference to FIGS. 22A˜F in this disclosure, upon the external drivingsignal being initially input at the first pin and second pin (e.g., uponinserting or plugging an LED lamp into a socket), the ballast interfacecircuit will not enter a conduction state until a period of delaypasses. In some embodiments, the period may be between about 10milliseconds (ms) and about 1 second. More specifically, in someembodiments, the period may be between about 10 ms and about 300 ms.

FIG. 22B is a block diagram of an LED lamp according to an exemplaryembodiment. Compared to FIG. 22A, ballast interface circuit 1510 in theembodiment of FIG. 22B is coupled between pin 503 and/or pin 504 andrectifying circuit 540. As explained regarding ballast interface circuit1510 in FIG. 22A, ballast interface circuit 1510 in FIG. 22B performsthe function of delaying the starting of the LED lamp, or causing theinput of the AC driving signal to be delayed for a predefined time, inorder to prevent the failure of starting by lamp driving circuits 505such as an electronic ballast.

Apart from coupling ballast interface circuit 1510 between terminalpin(s) and rectifying circuit in the above embodiments, ballastinterface circuit 1510 may alternatively be included within a rectifyingcircuit with a different structure. FIG. 22C illustrates an arrangementwith a ballast interface circuit in an LED lamp according to anexemplary embodiment. Referring to FIG. 22C, the rectifying circuit hasthe circuit structure of rectifying circuit 810 in FIG. 15C. Rectifyingcircuit 810 includes rectifying unit 815 and terminal adapter circuit541. Rectifying unit 815 is coupled to pins 501 and 502, terminaladapter circuit 541 is coupled to filtering output terminals 511 and512, and the ballast interface circuit 1510 in FIG. 22C is coupledbetween rectifying unit 815 and terminal adapter circuit 541. In thiscase, in the initial stage upon activation of the ballast, an AC drivingsignal as an external driving signal is input to the LED tube lamp,where the AC driving signal can only reach rectifying unit 815, butcannot reach other circuits such as terminal adapter circuit 541, otherinternal filter circuitry, and the LED lighting module. Moreover,parasitic capacitors associated with rectifying diodes 811 and 812within rectifying unit 815 are quite small in capacitance and may beignored. Accordingly, lamp driving circuit 505 in the initial stageisn't loaded with or effectively connected to the equivalent capacitoror inductor of the power supply module of the LED lamp, and the qualityfactor (Q) of lamp driving circuit 505 is therefore not adverselyaffected in this stage, resulting in a successful starting of the LEDlamp by lamp driving circuit 505. For example, the first rectifyingcircuit 510 may comprise a rectifying unit 815 and a terminal adaptercircuit 541, and the rectifying unit is coupled to the terminal adaptercircuit and is capable of performing half-wave rectification. In thisexample, the terminal adapter circuit is configured to transmit theexternal driving signal received via at least one of the first pin andthe second pin.

In one embodiment, under the condition that terminal adapter circuit 541doesn't include components such as capacitors or inductors,interchanging rectifying unit 815 and terminal adapter circuit 541 inposition, meaning rectifying unit 815 is connected to filtering outputterminals 511 and 512 and terminal adapter circuit 541 is connected topins 501 and 502, doesn't affect or alter the function of ballastinterface circuit 1510.

Further, as explained in FIGS. 15A˜15D, when a rectifying circuit isconnected to pins 503 and 504 instead of pins 501 and 502, thisrectifying circuit may constitute the rectifying circuit 540. Forexample, the circuit arrangement with a ballast interface circuit 1510in FIG. 22C may be alternatively included in rectifying circuit 540instead of rectifying circuit 810, without affecting the function ofballast interface circuit 1510.

In some embodiments, as described above terminal adapter circuit 541doesn't include components such as capacitors or inductors. Or whenrectifying circuit 610 in FIG. 15A constitutes the rectifying circuit510 or 540, parasitic capacitances in the rectifying circuit 510 or 540are quite small and may be ignored. These conditions contribute to notaffecting the quality factor of lamp driving circuit 505.

FIG. 22D is a block diagram of an LED lamp according to an exemplaryembodiment. Compared to the embodiment of FIG. 22A, ballast interfacecircuit 1510 in the embodiment of FIG. 22D is coupled between rectifyingcircuit 540 and filtering circuit 520. Since rectifying circuit 540 alsodoesn't include components such as capacitors or inductors, the functionof ballast interface circuit 1510 in the embodiment of FIG. 22D will notbe affected.

FIG. 22E is a block diagram of an LED lamp according to an exemplaryembodiment. Compared to the embodiment of FIG. 22A, ballast interfacecircuit 1510 in the embodiment of FIG. 22E is coupled between rectifyingcircuit 510 and filtering circuit 520. Similarly, since rectifyingcircuit 510 doesn't include components such as capacitors or inductors,the function of ballast interface circuit 1510 in the embodiment of FIG.22E will not be affected. Still, under the configuration shown in FIG.22E, the reception of a driving signal for driving an LED lamp (in thiscase a rectified driving signal) can be delayed. For example, in FIG.22E, the reception of a driving signal at a filter circuit 520 may bedelayed after the LED lamp is plugged in. The delay may be controlled bya ballast interface circuit.

As disclosed herein, the LED tube lamp may comprise a light stripattached to an inner surface of the lamp tube and which comprises abendable circuit sheet. And the LED lighting module may comprise an LEDmodule, which comprises an LED component (e.g., an LED or group of LEDs)and is disposed on the bendable circuit sheet. The ballast interfacecircuit may be between a ballast of an external power supply and the LEDlighting module and/or LED module of the LED tube lamp. The ballastinterface circuit may be configured to receive a signal derived from theexternal driving signal. For example, the signal may be a filteredsignal passed through a rectifying circuit and a filtering circuit.

Referring to FIG. 22F, the ballast interface circuit 1910 comprisesresistors 1913, 1916 and 1917, a capacitor 1914, a control circuit 1918,and a switch 1919. One end of the resistor 1913 is coupled to a firstrectifying output terminal 511, the other end is coupled to one end ofthe capacitor 1914, and the other end of the capacitor 1914 is coupledto a second rectifying output terminal 512. A connection node of theresistor 1913 and the capacitor 1914 is coupled to the control circuit1918 to provide power to the control circuit 1918 for operation. Theresistors 1916 and 1917 are connected in series between the firstrectifying output terminal 511 and the second rectifying output terminal512, and generates a detection signal indicative of an external ACsignal based on a voltage level of a rectified signal to the controlcircuit 1918. A control end of the switch 1919 is coupled to the controlcircuit 1918, and is turned on/off based on the control of the controlcircuit 1918. Two ends of the switch 1919 are coupled to ballastinterface circuit terminals 1911 and 1921.

When the control circuit 1918 determines that the voltage level of thedetection signal, generated by the resistors 1916 and 1917, is lowerthan a high determination level, the control circuit 1918 cuts theswitch 1919 off. When the electronic ballast has just started, thevoltage level of the output AC signal is not high enough and so thevoltage level of detection signal is lower than the high determinationlevel, the control circuit 1918 controls the switch 1919 on anopen-circuit state. At this moment, the LED is open-circuited and stopsoperating. When the voltage level of the output AC signal rises to reacha sufficient amplitude (which is a defined level) in a time period, thevoltage level of the detection signal is cyclically higher than the highdetermination level, the control circuit 1918 controls the switch 1919to keep on a conduction state, and so the LED operates normally.

When an electronic ballast is applied, a level of an AC signal generatedby the electronic ballast may range from about 200 to about 300 voltsduring the starting period (e.g., a time period shorter than 100 ms),and usually range from about 20 to about 30 ms and then the electronicballast enters an normal state and the level of the AC signal is raisedabove the 300 volts. In some embodiments, a resistance of the resistor1916 may range from about 200K to about 500K ohms; and in someembodiments from about 300K to about 400K ohms; a resistance of theresistor 1917 may range from about 0.5K to about 4 Kohms, and in someembodiments range from about 1.0K to 3K ohms; the high determinationlevel may range from 0.9 to 1.25 volts, and in some embodiments be about1.0 volts.

In some embodiments, the ballast interface circuit could be applicableto detect the inductive ballast. A characteristic of the inductiveballast is its current or voltage periodically crosses zero value as thecurrent or voltage signal proceeds with time. When the inductive ballastis applied, the level of the detection signal generated by the resistors1916 and 1917 is lower than a low determination level during thestarting period powered by the commercial power, the control circuit2018 controls the switch 1919 to keep on the conduction state and theLED tube lamp operates normally. In some embodiments, the lowdetermination level is lower than 0.2 volts, and in some embodimentslower than 0.1 volts.

For example, in some embodiments, during the starting period, if thedetection signal is higher than the low determination level and lowerthan the high determination level (the high determination level ishigher than the low determination level), the control circuit 2018controls the switch 1919 to be cut off. On the other hand, when thedetection signal is lower than the low determination level or higherthan the high determination level, the control circuit 2018 controls theswitch 1919 to be conducted continuously. Hence, the LED tube lamp usingthe ballast interface circuit can normally operate to emit lightregardless of whether the electronic ballast or the inductive ballast isapplied.

The resistors 1916 and 1917 are used to detect the level of the externalAC signal, and in certain applications, a frequency detection circuitmay be used to replace the voltage detection circuit of the resistors1916 and 1917. In general, the output signal of the electronic ballasthas a frequency higher than 20 Khz, and that of the inductive ballast islower than 400 Hz. By setting an appropriate frequency value, thefrequency detection circuit could properly determine that an electronicballast or an inductive ballast is applied, and so make the LED tubelamp operate normally to emit light.

FIG. 23A is a schematic diagram of a mode determination circuitaccording to some exemplary embodiments. FIG. 23B is a schematic diagramof an LED tube lamp including the exemplary mode determination circuitof FIG. 23A according to some exemplary embodiments. Referring to FIGS.23A and 23B, mode determination circuit 2010 may be coupled to arectifying circuit (e.g., the rectifying circuit 510 as illustrated inthe previous figures), for receiving a rectified signal. In thisexemplary embodiment, the mode determination circuit 2010 has twofunctions of allowing a continual current to flow through the LED unit632 and regulating the continuity of current to flow through the LEDunit 632. The mode determination circuit 2010 detects a state of aproperty of the rectified signal and selectively determines whether toperform a first mode or a second mode of lighting operation according tothe state of the property of the rectified signal. When performing thefirst mode of lighting operation, the mode determination circuit 2010allows a continual current, which in some embodiments may be acontinuous current without cessation, to flow through the LED unit 632until the external driving signal is disconnected from the LED tubelamp. When performing the second mode of lighting, the modedetermination circuit 2010 regulates the continuity of current to flowthrough the LED unit 632, for example by allowing a discontinuouscurrent to flow through the LED unit 632.

The mode determination circuit 2010 includes a first voltage divider201, a second voltage divider 202, a resistor 2019, a capacitor 2020 anda control circuit 2018. The first voltage divider 201 includes a firstresistor depicted in FIGS. 23A and 23B as resistor 2012, and a secondresistor depicted in FIGS. 23A and 23B as resistor 2013. The resistor2012 is connected to the resistor 2013 between the first output terminal511 and the second output terminal 512. For example, one end of thefirst resistor 2012 is connected to a connection node C to which thefirst output terminal 511 is connected and the opposite end of the firstresistor 2012 is connected to a connection node D to which one end ofthe second resistor 2013 is connected. In some embodiments, the oppositeend of the second resistor 2013 is connected to the second outputterminal 512 via at least a diode 2022 included in the first voltagedivider 201, but the disclosure is not limited thereto. In someembodiments, the opposite end of the second resistor 2013 may bedirectly connected to the second output terminal 512. The second voltagedivider 202 includes a third resistor depicted in FIGS. 23A and 23B asresistor 2014, and a fourth resistor depicted in FIGS. 23A and 23B asresistor 2015. The resistor 2014 is connected to the resistor 2015between the first output terminal 511 and the second output terminal512. For example, one end of the third resistor 2014 is connected to aconnection node C to which the first output terminal 511 is connectedand the opposite end of the third resistor 2014 is connected to aconnection node E to which one end of the fourth resistor 2015 isconnected. In some embodiments, the opposite end of the fourth resistor2015 is directly connected to the second output terminal 512. Thecontrol circuit 2018 is coupled between the first voltage divider 201and the LED unit 632, and the control circuit 2018 is also coupledbetween the second voltage divider 202 and the LED unit 632.

Referring to FIGS. 23A and 23B, in some embodiments, the modedetermination circuit may not be coupled to a rectifying circuit. Thus,when the mode determination circuit 2010 is not coupled with arectifying circuit, the mode determination circuit 2010 may detect astate of a property of the external driving signal (e.g., unrectifiedexternal driving signal) and selectively determines whether to perform afirst mode or a second mode of lighting operation according to the stateof the property of the external driving signal. When performing thefirst mode of lighting operation, the mode determination circuit 2010allows a continual current, which in some embodiments may be acontinuous current without cessation, to flow through the LED unit 632until the external driving signal is disconnected from the LED tube lampor a current generated from the input external driving signal is stoppedfrom passing through the LED unit 632 as a result of any intended orunintended operation(s) of the LED tube lamp. When performing the secondmode of lighting, the mode determination circuit 2010 regulates thecontinuity of current to flow through the LED unit 632, for example byallowing a discontinuous current to flow through the LED unit 632.

In some embodiments, the control circuit 2018 may be any circuit thathas a function of controlling, for instance, a CPU or a MCU. The controlcircuit 2018 in this embodiment is an IC module having an input terminalVCC, an input terminal STP, an input terminal CS, an output terminal2011 and an output terminal 2021. The input terminal VCC is connected toa connection node between the resistor 2019 and the capacitor 2020 forobtaining power from the rectifying circuit 510 for operation of the ICmodule. The output terminal 2011 is connected to a reference voltagesuch as the ground potential. The other output terminal 2021 is coupledto the LED unit 632. The first voltage divider 201 is configured forreceiving the rectified signal from the rectifying circuit 510 toproduce a first fraction voltage of the rectified signal at a connectionnode D between the first resistor 2012 and the second resistor 2013. Theinput terminal STP is connected to the connection node D. The controlcircuit 2018 receives the first fraction voltage at the terminal STP anddetermines whether to perform the first mode of lighting operationaccording to the first fraction voltage. In the first mode of lightingoperation, the control circuit 2018 provides a continuous current at theoutput terminal 202 to allow the continual current to flow through theLED unit 632. The second voltage divider 202 is used for receiving therectified signal from the rectifying circuit 510 to produce a secondfraction voltage of the rectified signal at a connection node E betweenthe third resistor 2014 and the fourth resistor 2015. The input terminalCS is connected to the connection node E. The control circuit 2018receives the second fraction voltage at the input terminal CS anddetermines whether to perform the second mode of lighting operationaccording to the second fraction voltage. In the second mode of lightingoperation, the control circuit 2018 provides a discontinuous current toregulate the continuity of the current to the LED unit 632.

In some embodiments, the control circuit 2018 includes a switchingcircuit 2024. The switching circuit 2024 is connected to the outputterminals 2011 and 2021 of the control circuit 2018 to achieve thefunctions of allowing the continual current to flow through the LED unit632 and regulating the continuity of current to flow through the LEDunit 632. When performing the first mode of lighting operation, thecontrol circuit 2018 allows the continuous current to flow through theLED unit 632 by continuously turning on, or maintaining an on state of,the switching circuit 2024. When performing the second mode of lightingoperation, the control circuit 2018 allows the discontinuous current toflow through the LED unit 632 by alternately turning on and off theswitching circuit 2024. The first mode of lighting operation may also bereferred to as continuous-conduction-mode (CCM) in which the current inan energy transfer circuit (which typically comprises inductor(s) and/orresistor(s)) connected to the LED unit 632 does not go to zero betweenswitching cycles of the switching circuit 2024. The second mode oflighting operation may also be referred to asdiscontinuous-conduction-mode (DCM) in which the current goes to zeroduring part of the switching cycle of the switching circuit 2014.

The switching circuit 2024 may include an electronic switch such as atransistor. The transistor may be a MOSFET, wherein the source terminalof the MOSFET is connected to the terminal 2011 to connect to areference voltage such as the ground potential, and the drain terminalof the MOSFET is connected to the terminal 2021 to couple to the LEDunit 632. Accordingly, in the first mode of lighting, the controlcircuit 2018 allows the continuous current to flow to the LED unit 632by continuously turning on, or maintaining an on state of, the MOSFET,and in the second mode of lighting, the control circuit 2018 allows thediscontinuous current to flow to the LED unit 632 by alternately turningon and off the MOSFET.

In some embodiments, the switching circuit 2024 may be a component ofthe LED tube lamp not included in control circuit 2018. If the LED tubelamp further includes the switching circuit 2024, the switching circuit2024 is coupled between the control circuit 2018 and the LED unit 632.

Accordingly, upon the LED lighting tube lamp being supplied by anelectrical ballast, the control circuit 2018 receives the first fractionvoltage at the terminal STP and determines whether the first fractionvoltage is in the first voltage range. If the first fraction voltage isin the first voltage range, the control circuit 2018 continuously turnson the switching circuit 2024 to allow a continuous current to flowthrough the LED unit 632 to perform the first mode of lighting. Inaddition, the control circuit 2018 receives the second fraction voltageat the terminal CS and determines whether the second fraction voltage isin the second voltage range. If the second fraction voltage is in thesecond voltage range, the control circuit 2018 alternately turns on andoff the switching circuit 2024 to allow the discontinuous current toflow through the LED unit 632 to perform the second mode of lighting.The control circuit 2018 performs the first mode and second mode oflighting until the external driving signal is disconnected from the LEDtube lamp. Once the LED tube lamp is started again, the control circuit2018 determines again whether to perform the first mode or the secondmode according to the first fraction voltage and the second fractionvoltage of the rectified signal.

In some embodiments, the first voltage range is defined to encompassvalues less than a first voltage value or larger than a second voltagevalue which is larger than the first voltage value. Thus, the controlcircuit 2018 performs the first mode of lighting if the first fractionvoltage is greater than the second voltage value or less than the firstvoltage value. For example, the first mode of lighting may comprise twofirst modes of lighting operations, and the control circuit 2018performs one of the two first modes of lighting operation when theexternal driving signal is provided by an electronic ballast to the STPterminal of the control circuit 2018. When the external signal isprovided by an electronic ballast to the STP terminal of the controlcircuit 2018, a voltage level at the STP terminal is larger than thesecond voltage value which is larger than the first voltage value. Thecontrol circuit 2018 performs the other of the two first modes oflighting operation when the external driving signal is provided by aninductive ballast to the STP terminal of the control circuit 2018. Whenthe external signal is provided by an inductive ballast to the STPterminal of the control circuit 2018, a voltage level at the STPterminal is less than the first voltage value. The first voltage valuemay be in some embodiments between 0 V and 0.5 V, and may be in someembodiments between 0 V and 0.1 V, and may be in some embodiments 0.1 V.The second voltage value is in some embodiments 1 V, and may be in someembodiments 1.2 V. The second voltage range is defined to encompassvalues larger than a third voltage value and less than a fourth voltagevalue which is larger than the third voltage value. The third voltagevalue may be in some embodiments between 0.5 V and 0.85 V, and may be insome embodiments between 0.7 V and 0.8 V, and may be in some embodimentsbetween 0.85 V and 1.0 V, and may be in some embodiments between 0.9 Vand 0.98 V, and may be 0.95 V in some embodiments.

In some embodiments, the LED tube lamp further includes an RC circuit203. The RC circuit 203 includes a resistor 2016 and a capacitor 2017. Afirst end of the resistor 2016 is connected to the connection node E. Asecond end of the resistor 2016 is connected to a first end of thecapacitor 2017 and the input terminal CS of the control circuit 2018. Asecond end of the capacitor 2017 is connected to the second outputterminal 512 of the rectifying circuit 510. The RC circuit 203 isconfigured to receive the second fraction voltage at node E. When thesecond fraction voltage is in the second voltage range, the capacitor2017 is charged and discharged repeatedly to produce a voltage variationat the first end of the capacitor 2017 to alternately turn on and offthe switching circuit 2024 to allow the discontinuous current to flowthrough the LED unit 632. Resistance value of resistor 2016 may bebetween 0.5 K and 4 K ohms, and may be in some embodiments between 1 Kand 3 K ohms, and may be in some embodiments 1K. Capacitance value ofthe capacitor 2017 may be in some embodiments between 1 nF and 500 nF,and may be in some embodiments between 20 nF and 30 nF, and may be insome embodiments 4.7 nF.

In some embodiments, the RC circuit 203 may be disposed with the secondvoltage divider 202. That is, the second voltage divider 202 includesthe resistors 2014 and 2015 and further includes the resistor 2016 andthe capacitor 2017. In other embodiments, the RC circuit 203 may be acomponent of the control circuit 2018. For example, the control circuit2018 may include the IC module and further may include the resistor 2016and the capacitor 2017. In this embodiment, the first end of thecapacitor 2017 is connected to the switching circuit 2024 to control theswitching circuit 2024.

Furthermore, in some embodiments, the RC circuit 203 may be replaced bya pulse width modulation circuit. The pulse width modulation circuit iscoupled between the switching circuit 2024 and the connection node E.The pulse width modulation circuits configured to receive the secondfraction voltage and then produce a pulse signal with a duty-cycleresponsive to the second fraction voltage, and the pulse signal is usedto alternately turning on and off the switching circuit 2024 to allowthe discontinuous current to flow to the LED unit 632.

In applications, when a first type of electronic ballast is applied,during the starting period (less than 100 ms, typically between about20-30 ms) of the LED tube lamp, the voltage at node C may be between200-300V, then the voltage at the node C rises when the ballast operatesin steady state, causing the first fraction voltage at node D rise. Whenthe second fraction voltage reaches the first voltage range, theswitching circuit 2024 is turned on and being kept in conduction state.In this situation, a constant current is provided to the LED unit 632.In some embodiments, resistance values of resistors 2012 and 2013 may be540 K ohms and 1 K ohms, respectively.

Similarly, when a second type of the electronic ballast is applied,during the starting period, the second fraction voltage at node E mayrise to reach the second voltage range when the electronic ballastoperates in steady state. Then the switching circuit 2024 is alternatelyturned on and off by the RC circuit 203 or the pulse width modulationcircuit. In this situation, a discontinuous current is provided to theLED unit 632. In some embodiments, resistance values of resistors 2014and 2015 may be 420 K ohms and 1 K ohms, respectively.

When an inductive ballast is applied, the characteristic of theinductive ballast is that its current or voltage periodically crosseszero value as the current or voltage signal proceeds with time. Duringthe starting period of the LED tube lamp powered by the commercialpower, the first fraction voltage produced by the first voltage divider201 may be less than the first voltage value which facilitates theswitching circuit 2024 to be turned on and maintain a conducting state.Therefore, the control circuit 2018 allows a constant current to flow tothe LED unit 632.

In some embodiments, the mode determination circuit 2010 comprises aballast interface circuit as an interface between the LED tube lamp andan electrical ballast used to supply the LED tube lamp. Accordingly, TheLED tube lamp can be applied to or be supplied by each of an electronicballast or an inductive ballast.

In addition, the mode determination circuit 2010 has another function ofbeing open-circuit for a period during the initial stage of starting theLED tube lamp for preventing the energy of the AC driving signal fromreaching the LED module 630. The mode determination circuit 2010 willnot enter a conduction state until a period of delay passes. The periodof delay may be a defined as a delay which is between about 10milliseconds and about 1 second.

In some embodiments, the LED tube lamp may include essentially nocurrent-limiting capacitor coupled in series to the LED unit 632. Forexample, an equivalent current-limiting capacitance coupled in series tothe LED unit 632 may be below about 0.1 nF.

In some embodiments, in order to stabilize the voltage at the node D,the mode determination circuit 2010 may further comprise a capacitorconnected in parallel with the resistor 2013. The capacitance of thecapacitor may be in some embodiments between 100 nF and 500 nF, and maybe in some embodiments between 200 nF to 300 nF, and may be in someembodiments 220 nF.

In some embodiments, the mode determination circuit 2010 may furthercomprises at least a diode 2022 coupled between the first voltagedivider 201 and the second output terminal 502. The voltage drop of thediode 2022 when electrically conducting is larger than the first voltagevalue. Thereby, the voltage level at node D is always larger than thefirst voltage value, such that the mode determination circuit 2010always performs the first mode of lighting with the first fractionvoltage higher than the second voltage value.

In some embodiments, in order to increase a voltage rating of the ICmodule, the mode determination circuit 2010 may further include adischarge tube 2023. Two ends of the discharge tube 2023 are connectedto the output terminal 2021 and the ground potential respectively. Avoltage rating of the discharge tube 2023 in some embodiments may bebetween 300 V and 600 V, and may be in some embodiments between 400 Vand 500V, and may be in some embodiments 400 V. In some embodiments, thedischarge tube 2023 also may be replaced by a thyristor.

In some embodiments, the property of the rectified signal may be thefrequency level or voltage level of the rectified signal. For example, afrequency detection circuit or other voltage detection circuits can beused to replace the voltage divider(s). Thus, the mode determinationcircuit 2010 can detect the voltage level or frequency level of therectified signal to determine whether to perform the first mode and thesecond mode of lighting.

Referring to FIG. 23B again, in order to reduce a pulse current resultfrom electrical ballasts, the LED tube lamp may further include a noisesuppressing circuit 570 coupled between the mode determination circuit2010 and the LED unit 632, and the noise suppressing circuit 570 isconnected in series with the LED unit 632. In some embodiments, thenoise-suppressing circuit 570 is an optional element and therefore maybe omitted. In one embodiment, if noise-suppressing circuit 570 isomitted, one end (i.e., the cathode as depicted in FIG. 23B) of LED unit632 is directly connected to the output terminal 2021 of the modedetermination circuit 2010.

In some embodiments, the noise suppressing circuit 570 includes aninductor 571 connected to the cathode of the LED unit 632 between theLED unit 632 and the output terminal 2021 of the mode determinationcircuit 2010 for reducing an abrupt change in the current provided tothe LED unit 632. However, a current flowing through the inductor 571may be larger than a current threshold, for instance, 0.35A. Therefore,an over-current may be generated and the inductor 571 may be overheateddue to the generation of the overcurrent. In order to eliminate theovercurrent, noise suppressing circuit 570 may further include aresistor 573, a resistor 574 and a transistor 575 to form anover-current protection circuit. The first terminal of the transistor575 is connected to a connection node between the LED unit 632 and theinductor 571 to connect to the first end of the inductor 571 to thecathode of the LED unit 632, the second terminal of the transistor 575(e.g., the gate terminal of the transistor 575) is connected to thesecond end of the inductor 571, and the third terminal of the transistor575 is coupled to the output terminal 2021 of the mode determinationcircuit 2010. The resistor 574 is connected between the third terminaland the second terminal of the transistor 575. The resistor 573 isconnected between the first terminal and the second terminal of thetransistor 575.

The over-current protection circuit will be triggered when the currentflowing through the inductor 571 is larger than a predefined currentthreshold. In general, the current from the LED unit 632 flows throughthe inductor 571 and resistor 574 thereby incurring a voltage dropacross the resistor 574. So, if the current increases, the voltage dropmay increase to reach a conducting voltage (e.g. 0.7 V) of thetransistor 575 thereby to turn on the transistor 575 to conduct current.Accordingly, when the transistor 575 operates in a conducting state, theconducting state of the transistor 575 diverts some current from flowingthrough the inductor 571 thus achieving the purpose of preventingexcessive current from flowing through the inductor 571. The transistor575 may comprise a BJT or a MOSFET. In some embodiments, the inductor571 may be connected in parallel with the anti-flickering circuit 550and 650 as depicted in FIGS. 20A and 20B, respectively. In someembodiments, inductance value of the inductor 571 may be between 1 mHand 10 mH, and may be in some embodiments between 1 mH and 8 mH, and maybe in some embodiments 6 mH.

In some embodiments, the noise-suppressing circuit 570 may furtherinclude a freewheel diode 572 for providing a current path. The cathodeof the free wheel diode 572 is connected to the cathode of the LED unit632 and the anode of the freewheel diode 572 is connected to the secondterminal (e.g., the gate terminal) of the transistor 575. A portion ofthe current flowing through the inductor 571 flows through the freewheeldiode 572.

In some embodiments, the freewheel diode 572, resistor 573, resistor 574and transistor 575 are optional elements and therefore can be omitted.In one embodiment, if freewheel diode 572, resistor 573, resistor 574and transistor 575 are omitted, the second end of the inductor 571 isdirectly connected to the output terminal 2021 of the mode determinationcircuit 2010.

In some embodiments, noise-suppressing circuit 570 may be connectedbetween a rectifying circuit 510 and the LED unit 632. In such cases,the function of the noise-suppressing circuit 570 will not be affected.

In some embodiments, the filtering circuit 520 may be coupled betweenthe mode determination circuit 2010 and the LED unit 632, and capacitor625 can be a component of the filtering circuit 520.

In various embodiments, the mode determination circuit 2010 may bereferred to as a ballast interface circuit. The ballast interfacecircuit may also be coupled to the first external connection terminaland the second external connection terminal between the lamp drivingcircuit 505 such as an electrical ballast and the LED unit 632 forreceiving an external driving signal from the electrical ballast fortransmitting power from the electrical ballast to the LED unit 632. Insome embodiments, the ballast interface circuit includes a detectingcircuit and a control circuit coupled to the detecting circuit. Thedetecting circuit detects a state of a property of the external drivingsignal. In some embodiments, the property of the external driving signalis the voltage level of the external driving signal. The detectingcircuit includes the first voltage divider 201 and the second voltagedivider 202 in FIG. 23A for receiving the external driving signal toobtain a first fraction voltage of the external driving signal and asecond fraction voltage of the external driving signal. The detectingcircuit determines whether the first fraction voltage is in the firstvoltage range, and determines whether the second fraction voltage is inthe second voltage range. According to the voltage level of externaldriving signal, the control circuit selectively determines to perform afirst mode or a second mode of lighting. When performing the first modeof lighting, the control circuit allows continual current to flowthrough the LED unit 632 until the external driving signal isdisconnected from the LED tube lamp; and when performing the second modeof lighting, the control circuit regulates the continuity of current toflow through the LED unit 632.

In other embodiments, the property of the external driving signal may bethe frequency level of the external driving signal. In variousembodiments, a frequency detection circuit or other voltage detectioncircuits can be used to replace the first voltage divider 201 and thesecond voltage divider 202. Accordingly, the ballast interface circuitcan detect the voltage level or the frequency level of the externaldriving signal to determine whether to perform the first mode and thesecond mode of lighting.

FIG. 23C is a schematic diagram of an LED tube lamp according to someembodiments, which includes an embodiment of the mode determinationcircuit 2010 of FIG. 23A. Compared to that shown in FIG. 23B, thepresent embodiment comprises the rectifying circuits 510 and 540, thecapacitor 625, the noise suppressing circuit 570, and the LED unit 632,and further includes two filament-simulating circuits 1760. Thefilament-simulating circuits 1760 are respectively coupled between thepins 501 and 502 and coupled between the pins 503 and 504. Thefilament-simulating circuit 1760 includes capacitors 1763 and 1764, andthe resistors 1765 and 1766. The capacitors 1763 and 1764 are connectedin series and coupled between the pins 503 and 504 and coupled betweenthe pins 501 and 502. The resistors 1765 and 1766 are connected inseries and coupled between the pins 503 and 504 and coupled between thepins 501 and 502. Furthermore, the connection node between thecapacitors 1763 and 1764 is coupled to that of the resistors 1765 and1766. Accordingly, the LED tube lamp in this embodiment can be appliedto or be supplied by programmed-start ballasts. When a programmed-startballast is applied, in a process of preheating, an AC current flowsthrough the capacitors 1763 and 1764 and resistors 1765 and 1766 toachieve the function of simulating the operation of actual filaments.Accordingly, the LED tube lamp is compatible with the programmed-startballast. That is, the programmed-start ballast can successfully startthe LED tube lamp in the embodiments.

Resistance values of resistors 1766 and 1765 may be between 10 K and 1 Mohms, and may be in some embodiments between 100 K and 1 M ohms, and maybe in some embodiments 100 K. Capacitance values of the capacitors 1763and 1764 may be in some embodiments between 3 nF and 2 pF, and may be insome embodiments 3 nF and 100 nF, and may be in some embodiments 4.7 nF.

In some embodiments, resistors 1766 and 1765 may be resistors withnegative temperature coefficient. If the filament-simulating circuits1760 includes resistors 1766 and 1765 with negative temperaturecoefficient, resistance value of the resistors 1766 and 1765 may be nogreater than 15 ohms, and may be in some embodiments between 2 to 10ohms, and may be in some embodiments between 4 ohms and 5 ohms.

In applications, with reference back to FIGS. 7 and 8, the filteringcircuit 520, one of the filament-simulating circuits 1760, therectifying circuit 510, anti-flickering circuit 550 and 650, and the LEDmodule 630 may be disposed on the long circuit sheet 251 of the LEDlight strip 2. The mode determination circuit 2010, anotherfilament-simulating circuit 1760, noise suppressing circuit 570, and therectifying circuit 540 may be disposed on the short circuit board 253.In some embodiments, if filtering circuit 520 includes the capacitor625, the capacitor 625 may be implemented by two film capacitorsconnected to each other and to be disposed on the long circuit sheet 251of the LED light strip 2. In some embodiments, both of thefilament-simulating circuits 1760 may be disposed on the short circuitboard 253 together. In one embodiment, the inductance 571 may bedisposed on the short circuit board 253 if the inductance value of theinductor 571 is 6 mH. This 6-mh inductor is too heavy to dispose on thelong circuit sheet 251 due to the difficulty of the manufacturing of thelong circuit sheet 251 with bendable structure.

With reference back to FIG. 5, welding defects may exist between thesoldering pads “a” of power supply 5 and soldering pads “b” of the LEDlight strip 2. Welding defects may block the intended current pathbetween the power supply 5 and the LED light strip 2(which light strip 2may comprise a flexible printed circuit board (FPC)) after supplyingpower, such that a high voltage (typically 600 V) exists between ananode electrode and cathode electrode of the power supply 5, or betweena anode electrode and a cathode electrode of the LED unit 632 on the LEDlight strip 2. Such high voltage causes the LED module 630 having one ormore LED unit 632 damages from sparkling or arcing.

To prevent (the effects caused by) arcing and sparkling, the LED tubelamp may include a discharge device 620. The discharge device 620 isdisposed on the circuit board and configured to connect in parallel withthe LED unit 632 (i.e., connected between anode and cathode electrodesof the LED unit 632) on the LED light strip 2. In a case that power issupplied normally, the LED 631 limits the voltage between the anode andcathode electrodes of the LED unit 632. Under such circumstances, thevoltage across the LED unit 632 may be less than 200 V. But, if weldingdefects exist, after the LED tube lamp is supplied by power, aninstantaneously high (e.g., larger than a predefined threshold voltage)voltage may occur across the anode and cathode electrodes of the LEDunit 632. Then, the discharge device 620 can discharge electricity toserve to prevent the instantaneously high voltage across the LED unit632 from being larger than the predefined threshold voltage. Thedischarge device 620 thus protects the LED unit 632 against arcing orsparkling due to the instantaneously high voltage across the LED unit632. In some embodiments, the discharge device 620 may be disposed onthe short circuit board 253.

The discharge device 620 may include a capacitor, a discharge tube, or adiode. The discharge device 620 may have a voltage rating in the rangeof about 1.2 to 5 times that of the LED unit 632. And the voltage ratingof the capacitor may be between 200-600 V, for example. In addition, ifthe discharge device 620 includes a capacitor, the capacitor can achievea function of filtering when power is normally supplied. In thisfunction, the discharge device 620 may be a component of the filteringcircuit 520.

FIG. 23D is a schematic diagram of an LED tube lamp according to someexemplary embodiments, which includes a protection circuit for providingovercurrent protection for the switching circuit 2024. With reference toFIG. 22F, FIG. 23A, and FIG. 23D, according to another aspect of presentdisclosure, to prevent the current flowing through the switch 1919(between ballast-compatible circuit terminals 1911 and 1921) orswitching circuit 2024 to be excessive (which causes heating up of, andincreases the risk of damaging, switch 1919 or switching circuit 2024,or shortening their life) due to the magnitude of current coming fromthe LED unit 632 to ballast-compatible circuit terminal 1911 or 1921 oroutput terminal 2011 or 2021, a protection circuit may be coupled inparallel to any of switch 1919 or switching circuit 2024, for providingovercurrent protection for the switch 1919 or the switching circuit2024. For example, the switch 1919 or the switching circuit 2024 may bearranged either as part of or outside of the control circuit 1918 orcontrol circuit 2018, respectively. Switch 1919 and switching circuit2024 may each comprise a first electronic switch such as a MOSFET 2024,and the protection circuit may comprise a second electronic switch fordiverting current from flowing through the first electronic switch whena current through the first electronic switch reaches a predefinedthreshold value, and an impedance element such as a resistor 2026. Thesecond electronic switch may comprise a transistor such as a bipolarjunction transistor 2025 coupled in parallel to the first electronicswitch 2024, wherein the bipolar junction transistor 2025 is configuredto divert some current from flowing through the first electronic switch2024 when the current through the first electronic switch 2024 reaches apredefined threshold value. In some embodiments, the bipolar junctiontransistor 2025 has its collector connected to a first terminal(drain/source) of the MOSFET 2024 and to the LED unit 632, and has abase connected to a second terminal (drain/source) of the MOSFET 2024; agate terminal of the MOSFET 2024 is controlled by the control circuit1918 or 2018; and the resistor 2026 is connected between the base andthe emitter of the bipolar junction transistor 2025. And a terminal ofthe control circuit 1918 or 2018, and the emitter of the bipolarjunction transistor 2025 may be connected to a reference voltage (suchas a ground potential) or the second rectifying output terminal 512. Insuch embodiments, the current from the LED unit 632 typically flowsthrough the first electronic switch 2024 and the added resistor 2026 ina circuit path, causing a voltage drop across the resistor 2026. Whenthe voltage across the resistor 2026 or between the base and emitterterminals of the bipolar junction transistor 2025 increases sufficiently(to for example about 0.7V) to cause the bipolar junction transistor2025 to conduct current, the bipolar junction transistor 2025 providesmore of a circuit path for the current flowing out of the firstelectronic switch 2024, thus achieving the purpose of reducing orlimiting the current through the first electronic switch 2024. In otherwords, upon the LED tube lamp receiving the external driving signal, thebipolar junction transistor 2025 will divert current from flowingthrough the first electronic switch 2024 as soon as a voltage across theresistor 2026 is sufficient to cause the bipolar junction transistor2025 to conduct current.

In various embodiments of the LED tube lamp according to thisdisclosure, each of the two end caps respectively coupled to twoopposite ends of the lamp tube may comprise at least one opening whichpenetrates through the end cap. In such case, (at least a component of)the protection circuit may preferably be positioned closer to the atleast one opening of the end cap than some other electronic componentsof the power supply (module) are, in order to facilitate heatdissipating or radiating by the protection circuit.

FIG. 24A is a block diagram of an LED tube lamp according to anexemplary embodiment. Compared to that shown in FIG. 14E, the presentembodiment comprises the rectifying circuits 510 and 540, the filteringcircuit 520, and the LED lighting module 530, and further comprises twofilament-simulating circuits 1560. The filament-simulating circuits 1560are respectively coupled between the pins 501 and 502 and coupledbetween the pins 503 and 504, for improving a compatibility with a lampdriving circuit having filament detection function, e.g., aprogrammed-start ballast.

In an initial stage upon the lamp driving circuit having filamentdetection function being activated, the lamp driving circuit willdetermine whether the filaments of the lamp operate normally or are inan abnormal condition of short-circuit or open-circuit. When determiningthe abnormal condition of the filaments, the lamp driving circuit stopsoperating and enters a protection state. In order to avoid that the lampdriving circuit erroneously determines the LED tube lamp to be abnormaldue to the LED tube lamp having no filament, the two filament-simulatingcircuits 1560 simulate the operation of actual filaments of afluorescent tube to have the lamp driving circuit enter into a normalstate to start the LED lamp normally.

FIG. 24B is a schematic diagram of a filament-simulating circuitaccording to an exemplary embodiment. The filament-simulating circuitcomprises a capacitor 1663 and a resistor 1665 connected in parallel.One end of the capacitor 1663 and one of the resistor 1665 are bothconnected to filament simulating terminal 1661 and the other end of thecapacitor 1663 and the other end of the resistor 1665 are both connectedto the filament simulating terminal 1662. Referring to FIG. 24A, thefilament simulating terminals 1661 and 1662 of the twofilament-simulating circuit 1660 are respectively coupled to the pins501 and 502 and the pins 503 and 504. During the filament detectionprocess, the lamp driving circuit outputs a detection signal to detectthe state of the filaments. The detection signal passes the capacitor1663 and the resistor 1665 and so the lamp driving circuit determinesthat the filaments of the LED lamp are normal.

In addition, a capacitance value of the capacitor 1663 is low and so acapacitive reactance (equivalent impedance) of the capacitor 1663 is farlower than an impedance of the resistor 1665 due to the lamp drivingcircuit outputting a high-frequency alternative current (AC) signal todrive LED lamp. Therefore, the filament-simulating circuit 1660 consumesrelatively low power when the LED lamp operates normally, and therefore,may not affect the luminous efficiency of the LED lamp.

FIG. 24C is a schematic diagram of a filament-simulating circuitaccording to another embodiment. A filament-simulating circuit 1760comprises capacitors 1763 and 1764, and the resistors 1765 and 1766. Thecapacitors 1763 and 1764 are connected in series and coupled between thefilament simulating terminals 1661 and 1662. The resistors 1765 and 1766are connected in series and coupled between the filament simulatingterminals 1661 and 1662. Furthermore, the connection node of capacitors1763 and 1764 is coupled to that of the resistors 1765 and 1766.Referring to FIG. 24A, the filament simulating terminals 1661 and 1662of the filament-simulating circuit 1760 are respectively coupled to thepins 501 and 502 and the pins 503 and 504. When the lamp driving circuitoutputs the detection signal for detecting the state of the filament,the detection signal passes the capacitors 1763 and 1764 and theresistors 1765 and 1766 so that the lamp driving circuit determines thatthe filaments of the LED lamp are normal.

In some embodiments, capacitance values of the capacitors 1763 and 1764are low and so a capacitive reactance of the serially connectedcapacitors 1763 and 1764 is far lower than an impedance of the seriallyconnected resistors 1765 and 1766 due to the lamp driving circuitoutputting the high-frequency AC signal to drive LED lamp. Therefore,the filament-simulating circuit 1760 consumes fairly low power when theLED lamp operates normally, and therefore, may not affect the luminousefficiency of the LED lamp. Moreover, whether any one of the capacitor1763 and the resistor 1765 is short circuited or open circuited, or anyone of the capacitor 1764 and the resistor 1766 is short circuited oropen circuited, the detection signal still passes through thefilament-simulating circuit 1760 between the filament simulatingterminals 1661 and 1662. Therefore, the filament-simulating circuit 1760still operates normally when any one of the capacitor 1763 and theresistor 1765 is short circuited or is an open circuit or any one of thecapacitor 1764 and the resistor 1766 is short circuited or is an opencircuit, and therefore, the filament-simulating circuit 1760demonstrates comparatively high fault tolerance. However, it should benoted that alternatively the connective line connecting the connectionnode of capacitors 1763 and 1764 and the connection node of theresistors 1765 and 1766 may be removed or not present, in which case thefilament-simulating circuit 1760 (without the connective line) stillperforms its filament-simulating function normally.

FIG. 25A is a block diagram of an LED tube lamp according to anexemplary embodiment. Compared to that shown in FIG. 14E, the presentembodiment comprises the rectifying circuits 510 and 540, the filteringcircuit 520, and the LED lighting module 530, and further comprises anover voltage protection (OVP) circuit 1570. The OVP circuit 1570 iscoupled to the filtering output terminals 521 and 522 for detecting thefiltered signal. The OVP circuit 1570 clamps the level of the filteredsignal when determining the level thereof higher than a predefined OVPvalue. Hence, the OVP circuit 1570 protects the LED lighting module 530from damage due to an OVP condition. The rectifying circuit 540 may beomitted and is therefore depicted by a dotted line.

FIG. 25B is a schematic diagram of an overvoltage protection (OVP)circuit according to an exemplary embodiment. The OVP circuit 1670comprises a voltage clamping diode 1671, such as a Zener diode, coupledto the filtering output terminals 521 and 522. The voltage clampingdiode 1671 is conducted to clamp a voltage difference at a breakdownvoltage when the voltage difference of the filtering output terminals521 and 522 (i.e., the level of the filtered signal) reaches thebreakdown voltage. The breakdown voltage may be in a range of about 40 Vto about 100 V. In some embodiments, the breakdown voltage may be in arange of about 55 V to about 75V.

FIG. 25C is a schematic diagram of an overvoltage protection (OVP)circuit according to an exemplary embodiment of the present invention.Referring to FIG. 25C, the over voltage protection circuit 1770comprises a symmetrical trigger diode 1771, resistors 1772, 1774 and1776, a capacitor 1733 and a switch 1775 (e.g., a transistor). Thesymmetrical trigger diode 1771, the resistor 1772 and the capacitor 1733are connected in series between a first filtering output terminal 521and a second filtering output terminal 522. One end of the symmetricaltrigger diode 1771 is coupled to the first filtering output terminal521, one end of the capacitor 1773 is coupled to the second filteringoutput terminal 522, and the resistor 1772 is coupled between thesymmetrical trigger diode 1771 and the capacitor 1773. The resistor 1774and the switch 1775 are connected in series between the first filteringoutput terminal 521 and the second filtering output terminal 522. Oneend of the resistor 1774 is coupled to the first filtering outputterminal 521, the other end is coupled to the switch 1775. One end ofthe switch 1775 is coupled to the second filtering output terminal 522,and one control end (e.g., the gate terminal of the switch 1775) iscoupled to a connection node of the resistor 1772 and the capacitor 1773through the resistor 1776. When a voltage difference of the firstfiltering output terminal 521 and the second filtering output terminal522(i.e., the voltage level of the filtered signal) reaches or is higherthan the breakover voltage of the symmetrical trigger diode 1771, thesymmetrical trigger diode 1771 is conducted, and so a voltage of thecapacitor 1773 is raised to trigger the switch 1775 to be conducted toprotect the LED lighting module 530.

In some embodiments, the breakover voltage of the symmetrical triggerdiode 1771 ranges from about 400 volts to about 1300 volts, in someembodiments from about 450 volts to about 700 volts, and in furtherembodiments from about 500 volts to about 600 volts.

FIG. 26A is a block diagram of an LED lamp according to an embodiment.Compared to FIG. 20A, the embodiment of FIG. 26A includes rectifyingcircuits 510 and 540, a filtering circuit 520, an LED lighting module530, and an anti-flickering circuit 550, and further includes aprotection circuit 560; wherein the power supply module may also includesome components of an LED lighting module 530. Protection circuit 560 iscoupled to filtering output terminals 521 and 522, to detect thefiltered signal from filtering circuit 520 for determining whether toenter a protection state. Upon entering a protection state, protectioncircuit 560 works to limit, restrain, or clamp down on the level of thefiltered signal, preventing damaging of components in LED lightingmodule 530. And rectifying circuit 540 and anti-flickering circuit 550may be omitted, as depicted by the dotted line in FIG. 26A.

FIG. 26B is a schematic diagram of the protection circuit according toan embodiment. Referring to FIG. 26B, a protection circuit 660 includesa voltage clamping circuit, a voltage division circuit, capacitors 663and 670, resistor 669, and a diode 672, for entering a protection statewhen a current and/or voltage of the LED module is/are or might beexcessively high, thereby preventing damaging of the LED module. Thevoltage clamping circuit includes a bidirectional triode thyristor(TRIAC) 661 and a DIAC or symmetrical trigger diode 662. The voltagedivision circuit includes bipolar junction transistors (BJT) 667 and 668and resistors 664, 665, 666, and 671.

Bidirectional triode thyristor 661 has a first terminal connected tofiltering output terminal 521, a second terminal connected to filteringoutput terminal 522, and a control terminal connected to a firstterminal of symmetrical trigger diode 662, which has a second terminalconnected to an end of capacitor 663, which has another end connected tofiltering output terminal 522. Resistor 664 is in parallel withcapacitor 663, and has an end connected to the second terminal ofsymmetrical trigger diode 662 and another end connected to filteringoutput terminal 522. Resistor 665 has an end connected to the secondterminal of symmetrical trigger diode 662 and another end connected tothe collector terminal of BJT 667, whose emitter terminal is connectedto filtering output terminal 522. Resistor 666 has an end connected tothe second terminal of symmetrical trigger diode 662 and another endconnected to the collector terminal of BJT 668 and the base terminal ofBJT 667. The emitter terminal of BJT 668 is connected to filteringoutput terminal 522. Resistor 669 has an end connected to the baseterminal of BJT 668 and another end connected to an end of capacitor670, which has another end connected to filtering output terminal 522.Resistor 671 has an end connected to the second terminal of symmetricaltrigger diode 662 and another end connected to the cathode of diode 672,whose anode is connected to filtering output terminal 521.

In some embodiments, the resistance of resistor 665 may be smaller thanthat of resistor 666.

Next, an exemplary operation of protection circuit 660 in overcurrentprotection is described as follows.

The node connecting resistor 669 and capacitor 670 is to receive acurrent detection signal S531, which represents the magnitude of currentthrough the LED module. The other end of resistor 671 is a voltageterminal 521′. In this embodiment concerning overcurrent protection,voltage terminal 521′ may be coupled to a biasing voltage source, or beconnected through diode 672 to filtering output terminal 521, as shownin FIG. 26B, to take a filtered signal as a biasing voltage source. Ifvoltage terminal 521′ is coupled to an external biasing voltage source,diode 672 may be omitted, so it is depicted in a dotted line in FIG.26B. The combination of resistor 669 and capacitor 670 can work tofilter out high frequency components of the current detection signalS531, and then input the filtered current detection signal S531 to thebase terminal of BJT 668 for controlling current conduction and cutoffof BJT 668. The filtering function of resistor 669 and capacitor 670 canprevent faulty operation of BJT 668 due to noise. In practical use,resistor 669 and capacitor 670 may be omitted, so they are each depictedin a dotted line in FIG. 26B. When they are omitted, current detectionsignal S531 is input directly to the base terminal of BJT 668.

When the LED lamp is operating normally and the current of the LEDmodule is within a normal range, BJT 668 is in a cutoff state, andresistor 66 works to pull up the base voltage of BJT 667, whichtherefore enters a conducting state. In this state, the electricpotential at the second terminal of symmetrical trigger diode 662 isdetermined based on the voltage at voltage terminal 521′ of the biasingvoltage source and voltage division ratios between resistor 671 andparallel-connected resistors 664 and 665. Since the resistance ofresistor 665 is relatively small, voltage share for resistor 665 issmaller and the electric potential at the second terminal of symmetricaltrigger diode 662 is therefore pulled down. Then, the electric potentialat the control terminal of bidirectional triode thyristor 661 is in turnpulled down by symmetrical trigger diode 662, causing bidirectionaltriode thyristor 661 to enter a cutoff state, which cutoff state makesprotection circuit 660 not being in a protection state.

When the current of the LED module exceeds an overcurrent value, thelevel of current detection signal S531 will increase to cause BJT 668 toenter a conducting state and then pull down the base voltage of BJT 667,which thereby enters a cutoff state. In this case, the electricpotential at the second terminal of symmetrical trigger diode 662 isdetermined based on the voltage at voltage terminal 521′ of the biasingvoltage source and voltage division ratios between resistor 671 andparallel-connected resistors 664 and 666. Since the resistance ofresistor 666 is relatively high, voltage share for resistor 666 islarger and the electric potential at the second terminal of symmetricaltrigger diode 662 is therefore higher. Then the electric potential atthe control terminal of bidirectional triode thyristor 661 is in turnpulled up by symmetrical trigger diode 662, causing bidirectional triodethyristor 661 to enter a conducting state, which conducting state worksto restrain or clamp down on the voltage between filtering outputterminals 521 and 522 and thus makes protection circuit 660 being in aprotection state.

In this embodiment, the voltage at voltage terminal 521′ of the biasingvoltage source is determined based on the trigger voltage ofbidirectional triode thyristor 661, and voltage division ratio betweenresistor 671 and parallel-connected resistors 664 and 665, or voltagedivision ratio between resistor 671 and parallel-connected resistors 664and 666. Through voltage division between resistor 671 andparallel-connected resistors 664 and 665, the voltage from voltageterminal 521′ at symmetrical trigger diode 662 will be lower than thetrigger voltage of bidirectional triode thyristor 661. Otherwise,through voltage division between resistor 671 and parallel-connectedresistors 664 and 666, the voltage from voltage terminal 521′ atsymmetrical trigger diode 662 will be higher than the trigger voltage ofbidirectional triode thyristor 661. For example, in some embodiments,when the current of the LED module exceeds an overcurrent value, thevoltage division circuit is adjusted to the voltage division ratiobetween resistor 671 and parallel-connected resistors 664 and 666,causing a higher portion of the voltage at voltage terminal 521′ toresult at symmetrical trigger diode 662, achieving a hysteresisfunction. Specifically, BJTs 667 and 668 as switches are respectivelyconnected in series to resistors 665 and 666 which determine the voltagedivision ratios. The voltage division circuit is configured to controlturning on which one of BJTs 667 and 668 and leaving the other off fordetermining the relevant voltage division ratio, according to whetherthe current of the LED module exceeds an overcurrent value. And theclamping circuit determines whether to restrain or clamp down on thevoltage of the LED module according to the applying voltage divisionratio.

Next, an exemplary operation of protection circuit 660 in overvoltageprotection is described as follows.

The node connecting resistor 669 and capacitor 670 is to receive acurrent detection signal S531, which represents the magnitude of currentthrough the LED module. As described above, protection circuit 660 stillworks to provide overcurrent protection. The other end of resistor 671is a voltage terminal 521′. In this embodiment concerning overvoltageprotection, voltage terminal 521′ is coupled to the positive terminal ofthe LED module to detect the voltage of the LED module. Takingpreviously described embodiments for example, in embodiments of FIGS.33A and 33B, LED lighting module 530 doesn't include driving circuit1530, and the voltage terminal 521′ would be coupled to filtering outputterminal 521. Whereas in embodiments of FIGS. 34A-34G, LED lightingmodule 530 includes driving circuit 1530, and the voltage terminal 521′would be coupled to driving output terminal 1521. In this embodiment,voltage division ratios between resistor 671 and parallel-connectedresistors 664 and 665, and voltage division ratios between resistor 671and parallel-connected resistors 664 and 666 will be adjusted accordingto the voltage at voltage terminal 521′, for example, the voltage atdriving output terminal 1521 or filtering output terminal 521.Therefore, normal overcurrent protection can still be provided byprotection circuit 660.

In some embodiments, when the LED lamp is operating normally, assumingovercurrent condition doesn't occur, the electric potential at thesecond terminal of symmetrical trigger diode 662 is determined based onthe voltage at voltage terminal 521′ and voltage division ratios betweenresistor 671 and parallel-connected resistors 664 and 665, and isinsufficient to trigger bidirectional triode thyristor 661. Thenbidirectional triode thyristor 661 is in a cutoff state, makingprotection circuit 660 not being in a protection state. On the otherhand, when the LED module is operating abnormally with the voltage atthe positive terminal of the LED module exceeding an overvoltage value,the electric potential at the second terminal of symmetrical triggerdiode 662 is sufficiently high to trigger bidirectional triode thyristor661 when the voltage at the first terminal of symmetrical trigger diode662 is larger than the trigger voltage of bidirectional triode thyristor661. Then bidirectional triode thyristor 661 enters a conducting state,making protection circuit 660 being in a protection state to restrain orclamp down on the level of the filtered signal.

As described above, protection circuit 660 provides one or two of thefunctions of overcurrent protection and overvoltage protection.

In some embodiments, protection circuit 660 may further include a zenerdiode connected to resistor 664 in parallel, which zener diode is usedto limit or restrain the voltage across resistor 664. The breakdownvoltage of the zener diode may be in the range of about 25˜50 volts. Insome embodiments, the breakdown voltage of the zener diode may be about36 volts.

Further, a silicon controlled rectifier may be substituted forbidirectional triode thyristor 661, without negatively affecting theprotection functions. Using a silicon controlled rectifier instead of abidirectional triode thyristor 661 has a lower voltage drop acrossitself in conduction than that across bidirectional triode thyristor 661in conduction.

In one embodiment, values of the parameters of protection circuit 660may be set as follows. Resistance of resistor 669 may be about 10 ohms.Capacitance of capacitor 670 may be about 1 nF. Capacitance of capacitor633 may be about 10 nF. The (breakover) voltage of symmetrical triggerdiode 662 may be in the range of about 26˜36 volts. Resistance ofresistor 671 may be in the range of about 300 k˜600 k ohms. In someembodiments, resistance of resistor 671 may be about 540 k ohms.Resistance of resistor 666 may be in the range of about 100 k˜300 kohms. In some embodiments, resistance of resistor 666 may be about 220 kohms. Resistance of resistor 665 may be in the range of about 30 k 100 kohms. In some embodiments, resistance of resistor 665 may be about 40 kohms. Resistance of resistor 664 is in some embodiments in the range ofabout 100 k˜300 k ohms, and, in certain embodiments, may be about 220 kohms. These values are example values, and the invention is not limitedto these values.

FIG. 27 is a schematic circuit diagram of an LED tube lamp according tosome embodiments including a protection circuit 760. Apart from theprotection circuit 560 and its embodiment 660 described in FIGS. 26A-B,protection circuit 760 is another embodiment, with other power supplycircuitry of LED tube lamp 500 being roughly or approximately embodiedin FIG. 27 for example. The LED tube lamp 500 including protectioncircuit 760 may include embodiments of some circuits and structures ofthe LED tube lamp described above, such as an LED module 630 includingan LED unit 632 including LEDs; the lamp tube having external connectionterminals or pins at one or two ends of the lamp tube; the filteringcircuit 520; the rectifying circuit 510 and/or 540; an inductive element576 (such as an inductor) connected in series with the LED unit 632; andfilament-simulating circuits 1560. In embodiments illustrated in FIG.27, the lamp tube has external connection terminals 501-504 at two endsof the lamp tube. These terminals 501-504 may be, for example, externalconnection pins. The filtering circuit 520 is represented by or includesa capacitor 625. The rectifying circuits 510 and 540 may respectivelyinclude diodes (constituting for example a full-wave rectifier circuitwhen the external driving signal is input across terminals 501-502 or503-504). Similar to inductor 571 shown in FIGS. 23B-C, inductiveelement 576 may be for reducing an abrupt change in the current providedto the LED unit 632. Or it may be for reducing/preventing EMI effects.Embodiments of filament-simulating circuits in FIG. 27 are twofilament-simulating circuits 2060. Each of the filament-simulatingcircuits 2060 includes a branch connected in parallel to a resistor 2063and comprising two series-connected capacitors 2061 and 2062, and isconnected between external connection terminals 501 and 502, or betweenexternal connection terminals 503 and 504. Although it may be that oneor more branches, each including one or more devices, offilament-simulating circuits 2060 are not regarded as (part of) afilament-simulating circuit in other practices in LED lightingindustries, they may function or be used for simulating a filament inthose practices.

As shown in FIG. 27, protection circuit 760 may be coupled between LEDmodules 630 and rectifying circuit 540; and protection circuit 760 iscoupled to rectifying circuit 510 and filtering circuit 520 as well, asis the case with protection circuit 560 in FIG. 26A. Protection circuit760 is for providing protection for the LED tube lamp, and may include acircuit branch (such as a voltage divider) comprising at least twoelements 761 and 763 connected in series between output terminals of therectifying circuit 510/540, for producing a signal at a connection nodebetween the two elements; and a control circuit 764 coupled to theconnection node between the two elements 761 and 763, for receiving,sampling, and/or detecting a state of the signal at the connection node.The terminal of the control circuit 764 that is coupled to theconnection node between the two elements 761 and 763 is denoted by “CS”in FIG. 27. The output terminals of the rectifying circuit 510/540 aredenoted by “A” and “B” in FIG. 27 and may be referred to as first andsecond output terminals respectively. The control circuit 764 includesor is coupled to a switching circuit 768 coupled to the rectifyingcircuit 510/540, and the switching circuit 768 is configured to betriggered on or off by the detected state, upon the external drivingsignal being input to the LED tube lamp, to allow discontinuous currentto flow through the LED unit 632. For example, as a result of theswitching circuit 768 being triggered on due to an overcurrent, acurrent flowing through the LED unit 632 may be temporarily cut off. Thecurrent may subsequently flow again after the switching circuit 768 istriggered off, which may result in a discontinuous current that isalternatingly on and off. From another perspective, the protectioncircuit 760 is configured such that when the external driving signal, asfrom an electrical ballast, is prone to result in an overcurrentcondition and is input to the LED tube lamp, for preventing anovercurrent condition the control circuit 764 is triggered by thedetected state to output a signal to a control terminal of the switchingcircuit 768 to turn on or conduct the switching circuit 768, wherein theconducting state of the switching circuit 768 may eventually prevent acurrent from flowing through the LED unit 632 (e.g., it may graduallydim or turn off the light emitted by the LED unit 632 when anovercurrent condition occurs). In various embodiments of protectioncircuit 760, the control circuit 764 may be implemented by an integratedcircuit for example. Accordingly, in some embodiments, the protectioncircuit 760 can provide overcurrent protection for the LED tube lamp,wherein the control circuit 764 is configured to be triggered by thedetected state, upon the external driving signal being input to the LEDtube lamp, to prevent the input external driving signal from resultingin an overcurrent condition to the LED tube lamp. And the detected stateof the signal at the connection node “CS” described above as triggeringthe control circuit 764 or the switching circuit 768 on may be forexample that a voltage or current at the connection node “CS” exceeds adefined threshold value.

Referring to FIG. 27, the at least two elements of the circuit branch orvoltage divider may comprise impedance elements 761 and 763 (such asresistors respectively) connected in series, for producing the signal ata connection node between the impedance elements 761 and 763. In thiscase, according to FIG. 27, the LED module 630 or LED unit 632 may beconnected between the first output terminal A of the rectifying circuit510/540 and the connection node between impedance elements 761 and 763.In some embodiments, the circuit branch or voltage divider may comprisean optional diode 762 connected between impedance elements 761 and 763.As shown in FIG. 27, diode 762 and impedance element 763 are connectedin series between the original connection node (between impedanceelements 761 and 763) and the second output terminal B of the rectifyingcircuit 510/540. In such a case, according to FIG. 27, the LED module630 or LED unit 632 may be connected between the first output terminal Aof the rectifying circuit 510/540 and the connection node between thediode 762 and the impedance element 763. The optional diode 762 may beused for increasing the voltage drop between the terminal “CS” (theoriginal connection node between impedance elements 761 and 763) and thesecond output terminal B of the rectifying circuit 510/540, for thevoltage at the terminal “CS” to be able to reach a designed thresholdvalue.

In embodiments of protection circuit 760 as illustrated in FIG. 27, theswitching circuit 768, which may be integrated into the control circuit764 as mentioned above, may comprise a transistor such as a MOSFET, andthus may have a control terminal connected to the control circuit 764(at the terminal denoted by “OUT” in FIG. 27), and two other terminalsconnected to a reference voltage and output terminal A of the rectifyingcircuit 510/540 respectively. In FIG. 27, a reference terminal of thecontrol circuit 764 is denoted by “GND”, and may be connected to thereference voltage, such as the ground potential or at the outputterminal B, as shown in FIG. 27. So the reference voltage may be of theoutput terminal B of the rectifying circuit 510/540. The LED tube lampmay further comprise an impedance element 765 (such as a resistor) andan impedance element 766 (such as a resistor) connected in seriesbetween the first and second output terminals A and B of the rectifyingcircuit 510/540, wherein a connection node between the impedanceelements 765 and 766 is coupled to the control circuit 764 (at aterminal denoted by “Vcc”) for supplying power to the control circuit764, as by the impedance elements 765 and 766 acting as a voltagedivider to produce a voltage at the connection node. The impedanceelements 765 and 766 may also be part of the protection circuit 760.Further, as shown in FIG. 27, there may be a capacitor 767 in the LEDtube lamp and coupled in parallel with the impedance element 766, andthe control circuit 764 is configured to be maintained in a workingstate by energy stored in the capacitor 767 upon the external drivingsignal being input to the LED tube lamp.

According to the above description, uses or operations of protectioncircuit 760 in and for the LED tube lamp are further explained asfollows with description of some embodiments. In embodiments of the LEDtube lamp including protection circuit 760 as illustrated in FIG. 27,when an electrical ballast, such as an electronic ballast, supplying theexternal driving signal to the LED tube lamp is working normally,typically meaning the ballast is supplying a current within a currentrange predefined for the LED module 630, and the input external drivingsignal results in a voltage at the connection node between the impedanceelements 765 and 766 being provided to the terminal “Vcc” to supply thecontrol circuit 764, the control circuit 764 is not triggered forprotecting from an overcurrent/overvoltage condition, and the LED tubelamp is in a lighting state due to a current flowing through the LEDunit 632. But when an electrical ballast supplying the external drivingsignal to the LED tube lamp is working abnormally or simply notcompatible with the LED tube lamp, or when the input external drivingsignal is from an electrical ballast and prone to result in theovercurrent condition, the control circuit 764 will be triggered by thedetected state to output a signal to the control terminal of theswitching circuit 768 to turn on or conduct the switching circuit 768,wherein the conducting state of the switching circuit 768 willeventually discontinue a current conduction through the LED unit 632. Atypical example of this case is: when such a ballast is supplying acurrent (nearly) above the current range and which causes a relativelylarge current flowing through the impedance element 763 and the optionaldiode 762, a resulting voltage between the terminal “CS” and the secondoutput terminal B of the rectifying circuit 510/540 will exceed thedefined threshold value so that the control circuit 764 is triggered(for protecting from the overcurrent condition) by the detected state ofthe resulting voltage to output a signal through the terminal “OUT” tothe control terminal of the switching circuit 768 to turn on or conductthe switching circuit 768. This conducting state of the switchingcircuit 768 in effect causes a short-circuit state between the first andsecond output terminals A and B of the rectifying circuit 510/540, whicheventually causes the current conduction through the LED unit 632, andthus the lighting state of the LED tube lamp, to be discontinued orstopped. In this case the switching circuit 768 is maintained in anon-state after being turned on, when the control circuit 764 ismaintained in a working state by energy stored in the capacitor 767; andthen the switching circuit 768 will be turned off when the controlcircuit 764 is not in a working state due to not receiving sufficientpower as from the capacitor 767. The control circuit 764 not receivingsufficient power may mean that the voltage at the connection nodebetween the impedance elements 765 and 766 or at the terminal “Vcc” isbelow a threshold value for maintaining the control circuit 764 in aworking state. This off-state of the switching circuit 768 when thecontrol circuit 764 becomes not in a working state may eventuallycontinue current conduction (e.g., exits an off or dimmed lighting stateto cause lighting or brighten lighting) through the LED unit 632 foremitting light. The resulting lighting state of the LED tube lamp uponcurrent conduction through the LED unit 632 being continued will causethe voltage at the terminal “Vcc” to increase, by a current flowingthrough the impedance elements 765 and 766, so as to reach the thresholdvalue causing the control circuit 764 to enter into a working stateagain (which may mean the control circuit 764 has received sufficientpower). And the off-state of the switching circuit 768 is maintaineduntil the control circuit 764 enters into a working state again due toreceiving sufficient power.

The lighting state of the LED tube lamp upon current conduction throughthe LED unit 632 being continued will proceed until another occasion ofovercurrent/overvoltage condition happens to cause a voltage (drop)between the terminal “CS” and the second output terminal B of therectifying circuit 510/540 to exceed the defined threshold value againso that the control circuit 764 is triggered (for protecting from theovercurrent/overvoltage condition) to turn on the switching circuit 768again, which will eventually discontinue the lighting state of the LEDtube lamp. Upon the control circuit 764 entering into a working stateagain, when the occasion of overcurrent/overvoltage condition happens,the control circuit 764 will be triggered by the detected state at theterminal “CS” to output a signal to the control terminal of theswitching circuit 768 to turn on or conduct the switching circuit 768again, eventually preventing a current from flowing through the LED unit632. According to the above description of how the protection circuit760 operates under different situations of the LED tube lamp beingsupplied by a normally working ballast or an abnormally working orunsuitable ballast (prone to cause overcurrent/overvoltage conditions),as mentioned above the switching circuit 768 may be triggered on or offby the detected state, upon the external driving signal being input tothe LED tube lamp, to allow discontinuous current to flow through theLED unit 632. The discontinuous current causes or reflects the switchingbetween the lighting state and the off-lighting state of the LED tubelamp, wherein the switching is due to a current conduction through theLED unit 632 being caused or discontinued as described above, and mayhappen alternately to result in flickering of the lighting of the LEDtube lamp.

Since embodiments of the protection circuit 760 described above in inFIG. 27 have the described detection function or role of detectingcurrent level going to the LED tube lamp, the protection circuit 760described above may be alternatively referred to as a detection circuit760 that can be used in a compatible LED tube lamp, for detection; andthen determining whether to prevent a current from flowing through theLED unit 632, or causing/allowing discontinuous current to flow throughthe LED unit 632.

Accordingly, advantages that may result from, or benefits of, usingembodiments of the protection/detection circuit 760 in variouscompatible LED tube lamps include the following. When the LED tube lampis being used with an incompatible electrical ballast as potentiallyhaving an overcurrent condition, performing flickering of the lightingof the LED tube lamp through the protection/detection circuit 760 canreduce temperature of the LED module 630 (since the lighting isdiscontinuous), and can serve to remind the users of the incompatibilityof the ballast with the subject LED tube lamp. The second benefit isthat since the external connection terminals 501-504 at two ends of thelamp tube may be connected to one or more (electrical or thermal) fuses(illustrated in FIG. 16D), each of the fuse can melt or blow when thecurrent going to the LED tube lamp exceeds a particular amperage whichmay cause its temperature to exceed a threshold, and the blowing of thefuse then breaks electrical and/or physical connection between the LEDtube lamp and the ballast to prevent electrical arcing or burning. Thethird advantage is that capacitance value of the capacitor 766 and/orresistance values of the resistors 765 and 766 can be adjusted todesirably adjust the frequency of the performed flickering of thelighting of the LED tube lamp. Other benefits include preventingoverheating or damaging of the LED tube lamp which could be caused by asurge. Moreover, the LED tube lamp using or including thedetection/protection circuit 760 may include, for example, an embodimentof ballast interface circuit 1510 which comprises a thyristor device orthyristor surge suppressor, positioned as between and in series with theLED unit 632 and impedance element 763 and whose delayed-conduction time(depending on when the thyristor device is triggered on) may be adjustedto adjust the frequency of the performed flickering of lighting of theLED tube lamp.

FIG. 28A is a block diagram of the driving circuit according to anembodiment of the present invention. Referring to FIG. 28A, the drivingcircuit includes a controller 1531, and a conversion circuit 1532 forpower conversion based on a current source, for driving the LED moduleto emit light. Conversion circuit 1532 includes a switching circuit 1535and an energy storage circuit 1538. And conversion circuit 1532 iscoupled to filtering output terminals 521 and 522 to receive and thenconvert a filtered signal, under the control by controller 1531, into adriving signal at driving output terminals 1521 and 1522 for driving theLED module. Under the control by controller 1531, the driving signaloutput by conversion circuit 1532 comprises a steady current, making theLED module emitting steady light.

FIG. 28B is a schematic diagram of the driving circuit according to anembodiment of the present invention. Referring to FIG. 28B, a drivingcircuit 1630 in this embodiment comprises a buck DC-to-DC convertercircuit having a controller 1631 and a converter circuit. The convertercircuit includes an inductor 1632, a diode 1633 for “freewheeling” ofcurrent, a capacitor 1634, and a switch 1635. Driving circuit 1630 iscoupled to filtering output terminals 521 and 522 to receive and thenconvert a filtered signal into a driving signal for driving an LEDmodule connected between driving output terminals 1521 and 1522.

In this embodiment, switch 1635 comprises a metal-oxide-semiconductorfield-effect transistor (MOSFET) and has a first terminal coupled to theanode of freewheeling diode 1633, a second terminal coupled to filteringoutput terminal 522, and a control terminal coupled to controller 1631used for controlling current conduction or cutoff between the first andsecond terminals of switch 1635. Driving output terminal 1521 isconnected to filtering output terminal 521, and driving output terminal1522 is connected to an end of inductor 1632, which has another endconnected to the first terminal of switch 1635. Capacitor 1634 iscoupled between driving output terminals 1521 and 1522, to stabilize thevoltage between driving output terminals 1521 and 1522. Freewheelingdiode 1633 has a cathode connected to driving output terminal 1521.

Next, a description follows as to an exemplary operation of drivingcircuit 1630.

Controller 1631 is configured for determining when to turn switch 1635on (in a conducting state) or off (in a cutoff state), according to acurrent detection signal S535 and/or a current detection signal S531.For example, in some embodiments, controller 1631 is configured tocontrol the duty cycle of switch 1635 being on and switch 1635 beingoff, in order to adjust the size or magnitude of the driving signal.Current detection signal S535 represents the magnitude of currentthrough switch 1635. Current detection signal S531 represents themagnitude of current through the LED module coupled between drivingoutput terminals 1521 and 1522. According to any of current detectionsignal S535 and current detection signal S531, controller 1631 canobtain information on the magnitude of power converted by the convertercircuit. When switch 1635 is switched on, a current of a filtered signalis input through filtering output terminal 521, and then flows throughcapacitor 1634, driving output terminal 1521, the LED module, inductor1632, and switch 1635, and then flows out from filtering output terminal522. During this flowing of current, capacitor 1634 and inductor 1632are performing storing of energy. On the other hand, when switch 1635 isswitched off, capacitor 1634 and inductor 1632 perform releasing ofstored energy by a current flowing from freewheeling capacitor 1633 todriving output terminal 1521 to make the LED module continuing to emitlight.

It's worth noting that capacitor 1634 is an optional element, so it canbe omitted and is thus depicted in a dotted line in FIG. 28B. In someapplication environments, the natural characteristic of an inductor tooppose instantaneous change in electric current passing through theinductor may be used to achieve the effect of stabilizing the currentthrough the LED module, thus omitting capacitor 1634.

FIG. 28C is a schematic diagram of the driving circuit according to anembodiment of the present invention. Referring to FIG. 28C, a drivingcircuit 1730 in this embodiment comprises a boost DC-to-DC convertercircuit having a controller 1731 and a converter circuit. The convertercircuit includes an inductor 1732, a diode 1733 for “freewheeling” ofcurrent, a capacitor 1734, and a switch 1735. Driving circuit 1730 isconfigured to receive and then convert a filtered signal from filteringoutput terminals 521 and 522 into a driving signal for driving an LEDmodule coupled between driving output terminals 1521 and 1522.

Inductor 1732 has an end connected to filtering output terminal 521, andanother end connected to the anode of freewheeling diode 1733 and afirst terminal of switch 1735, which has a second terminal connected tofiltering output terminal 522 and driving output terminal 1522.Freewheeling diode 1733 has a cathode connected to driving outputterminal 1521. And capacitor 1734 is coupled between driving outputterminals 1521 and 1522.

Controller 1731 is coupled to a control terminal of switch 1735, and isconfigured for determining when to turn switch 1735 on (in a conductingstate) or off (in a cutoff state), according to a current detectionsignal S535 and/or a current detection signal S531. When switch 1735 isswitched on, a current of a filtered signal is input through filteringoutput terminal 521, and then flows through inductor 1732 and switch1735, and then flows out from filtering output terminal 522. During thisflowing of current, the current through inductor 1732 increases withtime, with inductor 1732 being in a state of storing energy, whilecapacitor 1734 enters a state of releasing energy, making the LED modulecontinuing to emit light. On the other hand, when switch 1735 isswitched off, inductor 1732 enters a state of releasing energy as thecurrent through inductor 1732 decreases with time. In this state, thecurrent through inductor 1732 then flows through freewheeling diode1733, capacitor 1734, and the LED module, while capacitor 1734 enters astate of storing energy.

It's worth noting that capacitor 1734 is an optional element, so it canbe omitted and is thus depicted in a dotted line in FIG. 28C. Whencapacitor 1734 is omitted and switch 1735 is switched on, the current ofinductor 1732 does not flow through the LED module, making the LEDmodule not emit light; but when switch 1735 is switched off, the currentof inductor 1732 flows through freewheeling diode 1733 to reach the LEDmodule, making the LED module emit light. Therefore, by controlling thetime that the LED module emits light, and the magnitude of currentthrough the LED module, the average luminance of the LED module can bestabilized to be above a defined value, thus also achieving the effectof emitting a steady light.

FIG. 28D is a schematic diagram of the driving circuit according to anembodiment of the present invention. Referring to FIG. 28D, a drivingcircuit 1830 in this embodiment comprises a buck DC-to-DC convertercircuit having a controller 1831 and a converter circuit. The convertercircuit includes an inductor 1832, a diode 1833 for “freewheeling” ofcurrent, a capacitor 1834, and a switch 1835. Driving circuit 1830 iscoupled to filtering output terminals 521 and 522 to receive and thenconvert a filtered signal into a driving signal for driving an LEDmodule connected between driving output terminals 1521 and 1522.

Switch 1835 has a first terminal coupled to filtering output terminal521, a second terminal coupled to the cathode of freewheeling diode1833, and a control terminal coupled to controller 1831 to receive acontrol signal from controller 1831 for controlling current conductionor cutoff between the first and second terminals of switch 1835. Theanode of freewheeling diode 1833 is connected to filtering outputterminal 522 and driving output terminal 1522. Inductor 1832 has an endconnected to the second terminal of switch 1835, and another endconnected to driving output terminal 1521. Capacitor 1834 is coupledbetween driving output terminals 1521 and 1522, to stabilize the voltagebetween driving output terminals 1521 and 1522.

Controller 1831 is configured for controlling when to turn switch 1835on (in a conducting state) or off (in a cutoff state), according to acurrent detection signal S535 and/or a current detection signal S531.When switch 1835 is switched on, a current of a filtered signal is inputthrough filtering output terminal 521, and then flows through switch1835, inductor 1832, and driving output terminals 1521 and 1522, andthen flows out from filtering output terminal 522. During this flowingof current, the current through inductor 1832 and the voltage ofcapacitor 1834 both increase with time, so inductor 1832 and capacitor1834 are in a state of storing energy. On the other hand, when switch1835 is switched off, inductor 1832 is in a state of releasing energyand thus the current through it decreases with time. In this case, thecurrent through inductor 1832 circulates through driving outputterminals 1521 and 1522, freewheeling diode 1833, and back to inductor1832.

It's worth noting that capacitor 1834 is an optional element, so it canbe omitted and is thus depicted in a dotted line in FIG. 28D. Whencapacitor 1834 is omitted, no matter whether switch 1835 is turned on oroff, the current through inductor 1832 will flow through driving outputterminals 1521 and 1522 to drive the LED module to continue emittinglight.

FIG. 28E is a schematic diagram of the driving circuit according to anembodiment of the present invention. Referring to FIG. 28E, a drivingcircuit 1930 in this embodiment comprises a buck DC-to-DC convertercircuit having a controller 1931 and a converter circuit. The convertercircuit includes an inductor 1932, a diode 1933 for “freewheeling” ofcurrent, a capacitor 1934, and a switch 1935. Driving circuit 1930 iscoupled to filtering output terminals 521 and 522 to receive and thenconvert a filtered signal into a driving signal for driving an LEDmodule connected between driving output terminals 1521 and 1522.

Inductor 1932 has an end connected to filtering output terminal 521 anddriving output terminal 1522, and another end connected to a first endof switch 1935. Switch 1935 has a second end connected to filteringoutput terminal 522, and a control terminal connected to controller 1931to receive a control signal from controller 1931 for controlling currentconduction or cutoff of switch 1935. Freewheeling diode 1933 has ananode coupled to a node connecting inductor 1932 and switch 1935, and acathode coupled to driving output terminal 1521. Capacitor 1934 iscoupled to driving output terminals 1521 and 1522, to stabilize thedriving of the LED module coupled between driving output terminals 1521and 1522.

Controller 1931 is configured for controlling when to turn switch 1935on (in a conducting state) or off (in a cutoff state), according to acurrent detection signal S531 and/or a current detection signal S535.When switch 1935 is turned on, a current is input through filteringoutput terminal 521, and then flows through inductor 1932 and switch1935, and then flows out from filtering output terminal 522. During thisflowing of current, the current through inductor 1932 increases withtime, so inductor 1932 is in a state of storing energy; but the voltageof capacitor 1934 decreases with time, so capacitor 1934 is in a stateof releasing energy to keep the LED module continuing to emit light. Onthe other hand, when switch 1935 is turned off, inductor 1932 is in astate of releasing energy and its current decreases with time. In thiscase, the current through inductor 1932 circulates through freewheelingdiode 1933, driving output terminals 1521 and 1522, and back to inductor1932. During this circulation, capacitor 1934 is in a state of storingenergy and its voltage increases with time.

It's worth noting that capacitor 1934 is an optional element, so it canbe omitted and is thus depicted in a dotted line in FIG. 28E. Whencapacitor 1934 is omitted and switch 1935 is turned on, the currentthrough inductor 1932 doesn't flow through driving output terminals 1521and 1522, thereby making the LED module not emit light. On the otherhand, when switch 1935 is turned off, the current through inductor 1932flows through freewheeling diode 1933 and then the LED module to makethe LED module emit light. Therefore, by controlling the time that theLED module emits light, and the magnitude of current through the LEDmodule, the average luminance of the LED module can be stabilized to beabove a defined value, thus also achieving the effect of emitting asteady light.

FIG. 28F is a block diagram of the driving circuit according to anembodiment of the present invention. Referring to FIG. 28F, the drivingcircuit includes a controller 2631, and a conversion circuit 2632 forpower conversion based on an adjustable current source, for driving theLED module to emit light. Conversion circuit 2632 includes a switchingcircuit 2635 and an energy storage circuit 2638. And conversion circuit2632 is coupled to filtering output terminals 521 and 522 to receive andthen convert a filtered signal, under the control by controller 2631,into a driving signal at driving output terminals 1521 and 1522 fordriving the LED module. Controller 2631 is configured to receive acurrent detection signal S535 and/or a current detection signal S539,for controlling or stabilizing the driving signal output by conversioncircuit 2632 to be above an objective current value. Current detectionsignal S535 represents the magnitude of current through switchingcircuit 2635. Current detection signal S539 represents the magnitude ofcurrent through energy storage circuit 2638, which current may be e.g.an inductor current in energy storage circuit 2638 or a current outputat driving output terminal 1521. Any of current detection signal S535and current detection signal S539 can represent the magnitude of currentlout provided by the driving circuit from driving output terminals 1521and 1522 to the LED module. Controller 2631 is coupled to filteringoutput terminal 521 for setting the objective current value according tothe voltage Vin at filtering output terminal 521. Therefore, the currentlout provided by the driving circuit or the objective current value canbe adjusted corresponding to the magnitude of the voltage Vin of afiltered signal output by a filtering circuit.

It's worth noting that current detection signals S535 and S539 can begenerated by measuring current through a resistor or induced by aninductor. For example, a current can be measured according to a voltagedrop across a resistor in conversion circuit 2632 the current flowsthrough, or which arises from a mutual induction between an inductor inconversion circuit 2632 and another inductor in its energy storagecircuit 2638.

The above driving circuit structures are especially suitable for anapplication environment in which the external driving circuit for theLED tube lamp includes electronic ballast. An electronic ballast isequivalent to a current source whose output power is not constant. In aninternal driving circuit as shown in each of FIGS. 28B-28E, powerconsumed by the internal driving circuit relates to or depends on thenumber of LEDs in the LED module, and could be regarded as constant.When the output power of the electronic ballast is higher than powerconsumed by the LED module driven by the driving circuit, the outputvoltage of the ballast will increase continually, causing the level ofan AC driving signal received by the power supply module of the LED lampto continually increase, so as to risk damaging the ballast and/orcomponents of the power supply module due to their voltage ratings beingexceeded. On the other hand, when the output power of the electronicballast is lower than power consumed by the LED module driven by thedriving circuit, the output voltage of the ballast and the level of theAC driving signal will decrease continually so that the LED tube lampfail to normally operate.

It's worth noting that the power needed for an LED lamp to work isalready lower than that needed for a fluorescent lamp to work. If aconventional control mechanism of e.g. using a backlight module tocontrol the LED luminance is used with a conventional driving system ofe.g. a ballast, a problem will probably arise of mismatch orincompatibility between the output power of the external driving systemand the power needed by the LED lamp. This problem may even causedamaging of the driving system and/or the LED lamp. To prevent thisproblem, using e.g. the power/current adjustment method described abovein FIG. 28F enables the LED (tube) lamp to be better compatible withtraditional fluorescent lighting system.

FIG. 28G is a graph illustrating the relationship between the voltageVin and the objective current value lout according to an embodiment ofthe present invention. In FIG. 28G, the variable Vin is on thehorizontal axis, and the variable lout is on the vertical axis. In somecases, when the level of the voltage Vin of a filtered signal is betweenthe upper voltage limit VH and the lower voltage limit VL, the objectivecurrent value lout will be about an initial objective current value. Theupper voltage limit VH is higher than the lower voltage limit VL. Whenthe voltage Vin increases to be higher than the upper voltage limit VH,the objective current value lout will increase with the increasing ofthe voltage Vin. During this stage, a situation that may be preferableis that the slope of the relationship curve increase with the increasingof the voltage Vin. When the voltage Vin of a filtered signal decreasesto be below the lower voltage limit VL, the objective current value loutwill decrease with the decreasing of the voltage Vin. During this stage,a situation that may be preferable is that the slope of the relationshipcurve decrease with the decreasing of the voltage Vin. For example,during the stage when the voltage Vin is higher than the upper voltagelimit VH or lower than the lower voltage limit VL, the objective currentvalue lout is in some embodiments a function of the voltage Vin to thepower of 2 or above, in order to make the rate of increase/decrease ofthe consumed power higher than the rate of increase/decrease of theoutput power of the external driving system. Thus, adjustment of theobjective current value lout is in some embodiments a function of thefiltered voltage Vin to the power of 2 or above.

In another case, when the voltage Vin of a filtered signal is betweenthe upper voltage limit VH and the lower voltage limit VL, the objectivecurrent value lout of the LED lamp will vary, increase or decrease,linearly with the voltage Vin. During this stage, when the voltage Vinis at the upper voltage limit VH, the objective current value lout willbe at the upper current limit IH. When the voltage Vin is at the lowervoltage limit VL, the objective current value lout will be at the lowercurrent limit IL. The upper current limit IH is larger than the lowercurrent limit IL. And when the voltage Vin is between the upper voltagelimit VH and the lower voltage limit VL, the objective current valuelout will be a function of the voltage Vin to the power of 1.

With the designed relationship in FIG. 28G, when the output power of theballast is higher than the power consumed by the LED module driven bythe driving circuit, the voltage Vin will increase with time to exceedthe upper voltage limit VH. When the voltage Vin is higher than theupper voltage limit VH, the rate of increase of the consumed power ofthe LED module is higher than that of the output power of the electronicballast, and the output power and the consumed power will be balanced orequal when the voltage Vin is at a high balance voltage value VH+ andthe current lout is at a high balance current value IH+. In this case,the high balance voltage value VH+ is larger than the upper voltagelimit VH, and the high balance current value IH+ is larger than theupper current limit IH. On the other hand, when the output power of theballast is lower than the power consumed by the LED module driven by thedriving circuit, the voltage Vin will decrease to be below the lowervoltage limit VL. When the voltage Vin is lower than the lower voltagelimit VL, the rate of decrease of the consumed power of the LED moduleis higher than that of the output power of the electronic ballast, andthe output power and the consumed power will be balanced or equal whenthe voltage Vin is at a low balance voltage value VL- and the objectivecurrent value lout is at a low balance current value IL−. In this case,the low balance voltage value VL− is smaller than the lower voltagelimit VL, and the low balance current value IL− is smaller than thelower current limit IL.

In some embodiments, the lower voltage limit VL is defined to be around90% of the lowest output power of the electronic ballast, and the uppervoltage limit VH is defined to be around 110% of its highest outputpower. Taking a common AC power line with a voltage range of 100-277volts and a frequency of 60 Hz as an example, the lower voltage limit VLmay be set at 90 volts (=100*90%), and the upper voltage limit VH may beset at 305 volts (=277*110%).

FIG. 29A is a schematic diagram of the mode switching circuit in an LEDlamp according to an embodiment of the present invention. Referring toFIG. 29A, a mode switching circuit 680 includes a mode switch 681suitable for use with the driving circuit 1630 in FIG. 28B. Referring toFIGS. 29A and 28B, mode switch 681 has three terminals 683, 684, and685, wherein terminal 683 is coupled to driving output terminal 1522,terminal 684 is coupled to filtering output terminal 522, and terminal685 is coupled to the inductor 1632 in driving circuit 1630.

When mode switching circuit 680 determines to perform a first drivingmode, mode switch 681 conducts current in a first conductive paththrough terminals 683 and 685 and a second conductive path throughterminals 683 and 684 is in a cutoff state. In this case, driving outputterminal 1522 is coupled to inductor 1632, and therefore driving circuit1630 is working normally, which working includes receiving a filteredsignal from filtering output terminals 521 and 522 and then transformingthe filtered signal into a driving signal, output at driving outputterminals 1521 and 1522 for driving the LED module.

When mode switching circuit 680 determines to perform a second drivingmode, mode switch 681 conducts current in the second conductive paththrough terminals 683 and 684 and the first conductive path throughterminals 683 and 685 is in a cutoff state. In this case, driving outputterminal 1522 is coupled to filtering output terminal 522, and thereforedriving circuit 1630 stops working, and a filtered signal is inputthrough filtering output terminals 521 and 522 to driving outputterminals 1521 and 1522 for driving the LED module, while bypassinginductor 1632 and switch 1635 in driving circuit 1630.

FIG. 29B is a schematic diagram of the mode switching circuit in an LEDlamp according to an embodiment of the present invention. Referring toFIG. 29B, a mode switching circuit 780 includes a mode switch 781suitable for use with the driving circuit 1630 in FIG. 28B. Referring toFIGS. 29B and 28B, mode switch 781 has three terminals 783, 784, and785, wherein terminal 783 is coupled to filtering output terminal 522,terminal 784 is coupled to driving output terminal 1522, and terminal785 is coupled to switch 1635 in driving circuit 1630.

When mode switching circuit 780 determines to perform a first drivingmode, mode switch 781 conducts current in a first conductive paththrough terminals 783 and 785 and a second conductive path throughterminals 783 and 784 is in a cutoff state. In this case, filteringoutput terminal 522 is coupled to switch 1635, and therefore drivingcircuit 1630 is working normally, which working includes receiving afiltered signal from filtering output terminals 521 and 522 and thentransforming the filtered signal into a driving signal, output atdriving output terminals 1521 and 1522 for driving the LED module.

When mode switching circuit 780 determines to perform a second drivingmode, mode switch 781 conducts current in the second conductive paththrough terminals 783 and 784 and the first conductive path throughterminals 783 and 785 is in a cutoff state. In this case, driving outputterminal 1522 is coupled to filtering output terminal 522, and thereforedriving circuit 1630 stops working, and a filtered signal is inputthrough filtering output terminals 521 and 522 to driving outputterminals 1521 and 1522 for driving the LED module, while bypassinginductor 1632 and switch 1635 in driving circuit 1630.

FIG. 29C is a schematic diagram of the mode switching circuit in an LEDlamp according to an embodiment of the present invention. Referring toFIG. 29C, a mode switching circuit 880 includes a mode switch 881suitable for use with the driving circuit 1730 in FIG. 28C. Referring toFIGS. 29C and 28C, mode switch 881 has three terminals 883, 884, and885, wherein terminal 883 is coupled to filtering output terminal 521,terminal 884 is coupled to driving output terminal 1521, and terminal885 is coupled to inductor 1732 in driving circuit 1730.

When mode switching circuit 880 determines to perform a first drivingmode, mode switch 881 conducts current in a first conductive paththrough terminals 883 and 885 and a second conductive path throughterminals 883 and 884 is in a cutoff state. In this case, filteringoutput terminal 521 is coupled to inductor 1732, and therefore drivingcircuit 1730 is working normally, which working includes receiving afiltered signal from filtering output terminals 521 and 522 and thentransforming the filtered signal into a driving signal, output atdriving output terminals 1521 and 1522 for driving the LED module.

When mode switching circuit 880 determines to perform a second drivingmode, mode switch 881 conducts current in the second conductive paththrough terminals 883 and 884 and the first conductive path throughterminals 883 and 885 is in a cutoff state. In this case, driving outputterminal 1521 is coupled to filtering output terminal 521, and thereforedriving circuit 1730 stops working, and a filtered signal is inputthrough filtering output terminals 521 and 522 to driving outputterminals 1521 and 1522 for driving the LED module, while bypassinginductor 1732 and freewheeling diode 1733 in driving circuit 1730.

FIG. 29D is a schematic diagram of the mode switching circuit in an LEDlamp according to an embodiment of the present invention. Referring toFIG. 29D, a mode switching circuit 980 includes a mode switch 981suitable for use with the driving circuit 1730 in FIG. 28C. Referring toFIGS. 29D and 28C, mode switch 981 has three terminals 983, 984, and985, wherein terminal 983 is coupled to driving output terminal 1521,terminal 984 is coupled to filtering output terminal 521, and terminal985 is coupled to the cathode of diode 1733 in driving circuit 1730.

When mode switching circuit 980 determines to perform a first drivingmode, mode switch 981 conducts current in a first conductive paththrough terminals 983 and 985 and a second conductive path throughterminals 983 and 984 is in a cutoff state. In this case, filteringoutput terminal 521 is coupled to the cathode of diode 1733, andtherefore driving circuit 1730 is working normally, which workingincludes receiving a filtered signal from filtering output terminals 521and 522 and then transforming the filtered signal into a driving signal,output at driving output terminals 1521 and 1522 for driving the LEDmodule.

When mode switching circuit 980 determines to perform a second drivingmode, mode switch 981 conducts current in the second conductive paththrough terminals 983 and 984 and the first conductive path throughterminals 983 and 985 is in a cutoff state. In this case, driving outputterminal 1521 is coupled to filtering output terminal 521, and thereforedriving circuit 1730 stops working, and a filtered signal is inputthrough filtering output terminals 521 and 522 to driving outputterminals 1521 and 1522 for driving the LED module, while bypassinginductor 1732 and freewheeling diode 1733 in driving circuit 1730.

FIG. 29E is a schematic diagram of the mode switching circuit in an LEDlamp according to an embodiment of the present invention. Referring toFIG. 29E, a mode switching circuit 1680 includes a mode switch 1681suitable for use with the driving circuit 1830 in FIG. 28D. Referring toFIGS. 29E and 28D, mode switch 1681 has three terminals 1683, 1684, and1685, wherein terminal 1683 is coupled to filtering output terminal 521,terminal 1684 is coupled to driving output terminal 1521, and terminal1685 is coupled to switch 1835 in driving circuit 1830.

When mode switching circuit 1680 determines to perform a first drivingmode, mode switch 1681 conducts current in a first conductive paththrough terminals 1683 and 1685 and a second conductive path throughterminals 1683 and 1684 is in a cutoff state. In this case, filteringoutput terminal 521 is coupled to switch 1835, and therefore drivingcircuit 1830 is working normally, which working includes receiving afiltered signal from filtering output terminals 521 and 522 and thentransforming the filtered signal into a driving signal, output atdriving output terminals 1521 and 1522 for driving the LED module.

When mode switching circuit 1680 determines to perform a second drivingmode, mode switch 1681 conducts current in the second conductive paththrough terminals 1683 and 1684 and the first conductive path throughterminals 1683 and 1685 is in a cutoff state. In this case, drivingoutput terminal 1521 is coupled to filtering output terminal 521, andtherefore driving circuit 1830 stops working, and a filtered signal isinput through filtering output terminals 521 and 522 to driving outputterminals 1521 and 1522 for driving the LED module, while bypassinginductor 1832 and switch 1835 in driving circuit 1830.

FIG. 29F is a schematic diagram of the mode switching circuit in an LEDlamp according to an embodiment of the present invention. Referring toFIG. 29F, a mode switching circuit 1780 includes a mode switch 1781suitable for use with the driving circuit 1830 in FIG. 28D. Referring toFIGS. 29F and 28D, mode switch 1781 has three terminals 1783, 1784, and1785, wherein terminal 1783 is coupled to filtering output terminal 521,terminal 1784 is coupled to driving output terminal 1521, and terminal1785 is coupled to inductor 1832 in driving circuit 1830.

When mode switching circuit 1780 determines to perform a first drivingmode, mode switch 1781 conducts current in a first conductive paththrough terminals 1783 and 1785 and a second conductive path throughterminals 1783 and 1784 is in a cutoff state. In this case, filteringoutput terminal 521 is coupled to inductor 1832, and therefore drivingcircuit 1830 is working normally, which working includes receiving afiltered signal from filtering output terminals 521 and 522 and thentransforming the filtered signal into a driving signal, output atdriving output terminals 1521 and 1522 for driving the LED module.

When mode switching circuit 1780 determines to perform a second drivingmode, mode switch 1781 conducts current in the second conductive paththrough terminals 1783 and 1784 and the first conductive path throughterminals 1783 and 1785 is in a cutoff state. In this case, drivingoutput terminal 1521 is coupled to filtering output terminal 521, andtherefore driving circuit 1830 stops working, and a filtered signal isinput through filtering output terminals 521 and 522 to driving outputterminals 1521 and 1522 for driving the LED module, while bypassinginductor 1832 and switch 1835 in driving circuit 1830.

FIG. 29G is a schematic diagram of the mode switching circuit in an LEDlamp according to an embodiment of the present invention. Referring toFIG. 29G, a mode switching circuit 1880 includes mode switches 1881 and1882 suitable for use with the driving circuit 1930 in FIG. 28E.Referring to FIGS. 29G and 28E, mode switch 1881 has three terminals1883, 1884, and 1885, wherein terminal 1883 is coupled to driving outputterminal 1521, terminal 1884 is coupled to filtering output terminal521, and terminal 1885 is coupled to freewheeling diode 1933 in drivingcircuit 1930. And mode switch 1882 has three terminals 1886, 1887, and1888, wherein terminal 1886 is coupled to driving output terminal 1522,terminal 1887 is coupled to filtering output terminal 522, and terminal1888 is coupled to filtering output terminal 521.

When mode switching circuit 1880 determines to perform a first drivingmode, mode switch 1881 conducts current in a first conductive paththrough terminals 1883 and 1885 and a second conductive path throughterminals 1883 and 1884 is in a cutoff state, and mode switch 1882conducts current in a third conductive path through terminals 1886 and1888 and a fourth conductive path through terminals 1886 and 1887 is ina cutoff state. In this case, driving output terminal 1521 is coupled tofreewheeling diode 1933, and filtering output terminal 521 is coupled todriving output terminal 1522. Therefore, driving circuit 1930 is workingnormally, which working includes receiving a filtered signal fromfiltering output terminals 521 and 522 and then transforming thefiltered signal into a driving signal, output at driving outputterminals 1521 and 1522 for driving the LED module.

When mode switching circuit 1880 determines to perform a second drivingmode, mode switch 1881 conducts current in the second conductive paththrough terminals 1883 and 1884 and the first conductive path throughterminals 1883 and 1885 is in a cutoff state, and mode switch 1882conducts current in the fourth conductive path through terminals 1886and 1887 and the third conductive path through terminals 1886 and 1888is in a cutoff state. In this case, driving output terminal 1521 iscoupled to filtering output terminal 521, and filtering output terminal522 is coupled to driving output terminal 1522. Therefore, drivingcircuit 1930 stops working, and a filtered signal is input throughfiltering output terminals 521 and 522 to driving output terminals 1521and 1522 for driving the LED module, while bypassing freewheeling diode1933 and switch 1935 in driving circuit 1930.

FIG. 29H is a schematic diagram of the mode switching circuit in an LEDlamp according to an embodiment of the present invention. Referring toFIG. 29H, a mode switching circuit 1980 includes mode switches 1981 and1982 suitable for use with the driving circuit 1930 in FIG. 28E.Referring to FIGS. 29H and 28E, mode switch 1981 has three terminals1983, 1984, and 1985, wherein terminal 1983 is coupled to filteringoutput terminal 522, terminal 1984 is coupled to driving output terminal1522, and terminal 1985 is coupled to switch 1935 in driving circuit1930. And mode switch 1982 has three terminals 1986, 1987, and 1988,wherein terminal 1986 is coupled to filtering output terminal 521,terminal 1987 is coupled to driving output terminal 1521, and terminal1988 is coupled to driving output terminal 1522.

When mode switching circuit 1980 determines to perform a first drivingmode, mode switch 1981 conducts current in a first conductive paththrough terminals 1983 and 1985 and a second conductive path throughterminals 1983 and 1984 is in a cutoff state, and mode switch 1982conducts current in a third conductive path through terminals 1986 and1988 and a fourth conductive path through terminals 1986 and 1987 is ina cutoff state. In this case, driving output terminal 1522 is coupled tofiltering output terminal 521, and filtering output terminal 522 iscoupled to switch 1935. Therefore, driving circuit 1930 is workingnormally, which working includes receiving a filtered signal fromfiltering output terminals 521 and 522 and then transforming thefiltered signal into a driving signal, output at driving outputterminals 1521 and 1522 for driving the LED module.

When mode switching circuit 1980 determines to perform a second drivingmode, mode switch 1981 conducts current in the second conductive paththrough terminals 1983 and 1984 and the first conductive path throughterminals 1983 and 1985 is in a cutoff state, and mode switch 1982conducts current in the fourth conductive path through terminals 1986and 1987 and the third conductive path through terminals 1986 and 1988is in a cutoff state. In this case, driving output terminal 1521 iscoupled to filtering output terminal 521, and filtering output terminal522 is coupled to driving output terminal 1522. Therefore, drivingcircuit 1930 stops working, and a filtered signal is input throughfiltering output terminals 521 and 522 to driving output terminals 1521and 1522 for driving the LED module, while bypassing freewheeling diode1933 and switch 1935 in driving circuit 1930.

It's worth noting that the mode switches in the above embodiments mayeach comprise, for example, a single-pole double-throw switch, orcomprise two semiconductor switches (such as metal oxide semiconductortransistors), for switching a conductive path on to conduct currentwhile leaving the other conductive path cutoff. Each of the twoconductive paths provides a path for conducting the filtered signal,allowing the current of the filtered signal to flow through one of thetwo paths, thereby achieving the function of mode switching orselection. For example, with reference to FIGS. 14A, 14B, and 14D inaddition, when the lamp driving circuit 505 is not present and the LEDtube lamp 500 is directly supplied by the AC power supply 508, the modeswitching circuit may determine on performing a first driving mode inwhich the driving circuit (such as driving circuit 1530, 1630, 1730,1830, or 1930) transforms the filtered signal into a driving signal of alevel meeting a required level to properly drive the LED module to emitlight. On the other hand, when the lamp driving circuit 505 is present,the mode switching circuit may determine on performing a second drivingmode in which the filtered signal is (almost) directly used to drive theLED module to emit light; or alternatively the mode switching circuitmay determine on performing the first driving mode to drive the LEDmodule to emit light.

The LED tube lamps according to various different embodiments of thepresent invention are described as above. With respect to an entire LEDtube lamp, the features including for example “adopting the bendablecircuit sheet as the LED light strip” and “utilizing the circuit boardassembly to connect the LED light strip and the power supply” may beapplied in practice singly or integrally such that only one of thefeatures is practiced or a number of the features are simultaneouslypracticed.

As an example, the feature “adopting the bendable circuit sheet as theLED light strip” may include “the connection between the bendablecircuit sheet and the power supply is by way of wire bonding orsoldering bonding; the bendable circuit sheet includes a wiring layerand a dielectric layer arranged in a stacked manner; the bendablecircuit sheet has a circuit protective layer made of ink to reflectlight and has widened part along the circumferential direction of thelamp tube to function as a reflective film.”

As an example, the feature “utilizing the circuit board assembly toconnect the LED light strip and the power supply” may include “thecircuit board assembly has a long circuit sheet and a short circuitboard that are adhered to each other with the short circuit board beingadjacent to the side edge of the long circuit sheet; the short circuitboard is provided with a power supply module to form the power supply;the short circuit board is stiffer than the long circuit sheet.”

According to examples of the power supply module, the external drivingsignal may be low frequency AC signal (e.g., commercial power), highfrequency AC signal (e.g., that provided by a ballast), or a DC signal(e.g., that provided by a battery), input into the LED tube lamp througha drive architecture of single-end power supply or dual-end powersupply. For the drive architecture of dual-end power supply, theexternal driving signal may be input by using only one end thereof assingle-end power supply.

The LED tube lamp may omit the rectifying circuit when the externaldriving signal is a DC signal.

According examples of the rectifying circuit in the power supply module,in certain embodiments, there may be a single rectifying circuit, ordual rectifying circuits. First and second rectifying circuits of thedual rectifying circuit may be respectively coupled to the two end capsdisposed on two ends of the LED tube lamp. The single rectifying circuitis applicable to the drive architecture of signal-end power supply, andthe dual rectifying circuit is applicable to the drive architecture ofdual-end power supply. Furthermore, the LED tube lamp having at leastone rectifying circuit is applicable to the drive architecture of lowfrequency AC signal, high frequency AC signal or DC signal.

The single rectifying circuit may be a half-wave rectifier circuit orfull-wave bridge rectifying circuit. The dual rectifying circuit maycomprise two half-wave rectifier circuits, two full-wave bridgerectifying circuits or one half-wave rectifier circuit and one full-wavebridge rectifying circuit.

According to examples of the pin in the power supply module, in certainembodiments, there may be two pins in a single end (the other end has nopin), two pins in corresponding ends of two ends, or four pins incorresponding ends of two ends. The designs of two pins in single endtwo pins in corresponding ends of two ends are applicable to signalrectifying circuit design of the of the rectifying circuit. The designof four pins in corresponding ends of two ends is applicable to dualrectifying circuit design of the of the rectifying circuit, and theexternal driving signal can be received by two pins in only one end orin two ends.

According to the design of the LED lighting module according to someembodiments, the LED lighting module may comprise the LED module and adriving circuit or only the LED module.

If there is only the LED module in the LED lighting module and theexternal driving signal is a high frequency AC signal, a capacitivecircuit may be in at least one rectifying circuit and the capacitivecircuit may be connected in series with a half-wave rectifier circuit ora full-wave bridge rectifying circuit of the rectifying circuit and mayserve as a current modulation circuit to modulate the current of the LEDmodule since the capacitor acts as a resistor for a high frequencysignal. Thereby, even when different ballasts provide high frequencysignals with different voltage levels, the current of the LED module canbe modulated into a defined current range for preventing over current.In addition, an energy-releasing circuit may be connected in parallelwith the LED module. When the external driving signal is no longersupplied, the energy-releasing circuit releases the energy stored in thefiltering circuit to lower a resonance effect of the filtering circuitand other circuits for restraining the flicker of the LED module.

In some embodiments, if there are the LED module and the driving circuitin the LED lighting module, the driving circuit may be a buck converter,a boost converter, or a buck-boost converter. The driving circuitstabilizes the current of the LED module at a defined current value, andthe defined current value may be modulated based on the external drivingsignal. For example, the defined current value may be increased with theincreasing of the level of the external driving signal and reduced withthe reducing of the level of the external driving signal. Moreover, amode switching circuit may be added between the LED module and thedriving circuit for switching the current from the filtering circuitdirectly or through the driving circuit inputting into the LED module.

According to some embodiments, the LED module comprises plural stringsof LEDs connected in parallel with each other, wherein each LED may havea single LED chip or plural LED chips emitting different spectrums. EachLEDs in different LED strings may be connected with each other to form amesh connection.

According to the design of the ballast interface circuit of the powersupply module in some embodiments, the ballast interface circuit may beconnected in series with the rectifying circuit. Under the design ofbeing connected in series with the rectifying circuit, the ballastinterface circuit is initially in a cutoff state and then changes to aconducting state in or after an objective delay. The ballast interfacecircuit makes the electronic ballast activate during the starting stageand enhances the compatibility for instant-start ballast. Furthermore,the ballast interface circuit maintains the compatibilities with otherballasts, e.g., programmed-start and rapid-start ballasts.

According to the design of the mode determination circuit in someembodiments, the mode determination circuit may be connected to therectifying circuit for detecting the state of the property of therectified signal to selectively determine whether to perform a firstmode or a second mode of lighting according to the state of the propertyof the rectified signal. Accordingly, the LED tube lamp is compatiblewith different types of the electrical ballasts, e.g. electronicballasts and inductive (or magnetic) ballasts.

According to the design of the mode determination circuit in someembodiments, the mode determination circuit may be connected to theelectrical ballast for detecting the state of the property of theexternal driving signal to selectively determine whether to perform afirst mode or a second mode of lighting according to the state of theproperty of the external driving signal. Accordingly, the LED tube lampis compatible with different types of the electrical ballasts, e.g.electronic ballasts and inductive ballasts.

According to the design of the mode determination circuit in someembodiments, the mode determination circuit includes a ballast interfacecircuit as an interface between the LED tube lamp and electrical ballastused to supply the LED tube lamp. Accordingly, the LED tube lamp iscompatible with different types of the electrical ballasts, e.g.electronic ballasts and inductive ballasts.

According to the design of the mode determination circuit in someembodiments, the mode determination circuit includes a discharge deviceto be conducted when welding defects existed between the positiveelectrodes of the LED unit and the negative electrodes of the LED unitfor preventing the LED unit from arcing.

The above-mentioned features can be accomplished in any combination toimprove the LED tube lamp, and the above embodiments are described byway of example only. The present invention is not herein limited, andmany variations are possible without departing from the spirit of thepresent invention and the scope as defined in the appended claims.

What is claimed is:
 1. A power source module for an LED lamp,comprising: a filament-simulating circuit electrically connected to afirst bi-pin terminal and a second bi-pin terminal of the LED lamp, eachof the first bi-pin terminal and the second bi-pin terminal configuredto allow a current to flow from one pin to the other pin via thefilament-simulating circuit during a pre-heat process executed by aballast; a current limiting circuit electrically connected to thefilament-simulating circuit and configured to limit a current from thefilament-simulating circuit; a first rectifier electrically connected tothe current limiting circuit and configured to rectify the current fromthe current limiting circuit; and a filter electrically connectedbetween the first rectifier and at least one LED of the LED lamp andconfigured to smooth the current from the first rectifier, wherein thefirst rectifier is electrically connected to the firstfilament-simulating circuit in parallel.
 2. The power source module ofclaim 1, wherein the filament-simulating circuit comprises a firstfilament-simulating circuit connected between two pins of the firstbi-pin terminal, and a second filament-simulating circuit connectedbetween two pins of the second bi-pin terminal; the firstfilament-simulating circuit comprises two pairs of series-connectedimpedance elements; and each pair of series-connected impedance elementsare connected between the two pins of the first bi-pin terminal.
 3. Thepower source module of claim 2, wherein each pair of series-connectedimpedance elements comprises a resistor or a capacitor.
 4. The powersource module of claim 1, wherein the first rectifier comprises a bridgerectifying circuit of four diodes.
 5. The power source module of claim1, wherein the current limiting circuit comprises at least a capacitor.6. The power source module of claim 1, wherein the current limitingcircuit comprises: a first capacitor, one end of the first capacitorbeing electrically connected to one pin of the first bi-pin terminal;and a second capacitor, one end of the second capacitor beingelectrically connected to the other pin of the first bi-pin terminal. 7.The power source module of claim 1, wherein the first rectifiercomprises two diodes electrically connected in series and a connectionnode connecting the two diodes is coupled to the current limitingcircuit, wherein a current flows from the at least one LED to one pin ofthe first bi-pin terminal through one of the two diodes and the currentlimiting circuit, or from one pin of the first bi-pin terminal to the atleast one LED through the other of the two diodes and the currentlimiting circuit.
 8. The power source module of claim 1, wherein the LEDlamp comprises an LED module comprising the at least one LED; thefilament-simulating circuit comprises a first filament-simulatingcircuit comprising an impedance element electrically connected betweentwo pins of the first bi-pin terminal, and a second filament-simulatingcircuit comprising an impedance element electrically connected betweentwo pins of the second bi-pin terminal; and the power source modulefurther comprises a second rectifier coupled between the secondfilament-simulating circuit and the LED module, wherein the secondrectifier is electrically connected to the second filament-simulatingcircuit in parallel and is electrically connected to the LED module. 9.An LED lamp, comprising: a current limiting circuit electricallyconnected to a first terminal of the LED lamp for limiting a currentfrom the first terminal; a first rectifier electrically connected to thecurrent limiting circuit for rectifying the current from the currentlimiting circuit; a filter electrically connected between the firstrectifier and at least one LED of the LED lamp for smoothing the currentfrom the first rectifier; and a filament-simulating circuit electricallyconnected to a first bi-pin terminal and a second bi-pin terminal of theLED lamp, each of the first and the second bi-pin terminals having acurrent flowing from one pin to the other pin of the respective bi-pinterminal via the filament-simulating circuit during a pre-heat processexecuted by a ballast, wherein the filament-simulating circuit comprisesa first filament-simulating circuit electrically connected between twopins of the first bi-pin terminal, and a second filament-simulatingcircuit electrically connected between two pins of the second bi-pinterminal, wherein the first rectifier comprises two diodes electricallyconnected in series, and the first rectifier is electrically connectedto the first filament-simulating circuit in parallel.
 10. The LED lampof claim 9, wherein the first filament-simulating circuit comprises twopairs of series-connected impedance elements; and each pair ofseries-connected impedance elements are connected between the two pinsof the first bi-pin terminal.
 11. The LED lamp of claim 9, wherein eachof the first filament-simulating circuit and second filament-simulatingcircuit comprises a resistor or a capacitor.
 12. The LED lamp of claim9, wherein the current limiting circuit comprises at least a capacitor.13. The LED lamp of claim 9, wherein the current limiting circuitcomprises a first capacitor, one end of the first capacitor beingelectrically connected to one pin of the first bi-pin terminal; and asecond capacitor, one end of the second capacitor being electricallyconnected to the other pin of the first bi-pin terminal.
 14. The LEDlamp of claim 9, further comprising an LED module comprising the atleast one LED, wherein the filament-simulating circuit comprises a firstfilament-simulating circuit comprising an impedance element electricallyconnected between two pins of the first bi-pin terminal and a secondfilament-simulating circuit comprising an impedance element electricallyconnected between two pins of the second bi-pin terminal; and a secondrectifier coupled between the second filament-simulating circuit and theLED module, wherein the second rectifier is electrically connected tothe second filament-simulating circuit in parallel and is electricallyconnected to the LED module.
 15. An LED lamp, comprising: a currentlimiting circuit electrically connected to a first terminal of the LEDlamp for limiting a current from the first terminal; a first rectifierelectrically connected to the current limiting circuit for rectifyingthe current from the current limiting circuit; a filter electricallyconnected between the first rectifier and at least one LED of the LEDlamp for smoothing the current from the first rectifier; a firstfilament-simulating circuit electrically connected to a first bi-pinterminal of the LED lamp, and a second filament-simulating circuitelectrically connected to a second bi-pin terminal of the LED lamp, eachof the first and the second bi-pin terminals arranged to have a currentflowing from one pin to the other pin of the respective bi-pin terminalvia the respective first or second filament-simulating circuit after theLED lamp is connected to a ballast and before a normal operation stateof the LED lamp, wherein the first filament-simulating circuit comprisestwo pairs of series-connected impedance elements; each pair ofseries-connected impedance elements are connected between two pins ofthe first bi-pin terminal; and a second rectifier electrically connectedto the second filament-simulating circuit in parallel and iselectrically connected to the at least one LED.
 16. The LED lamp ofclaim 15, wherein each pair of series-connected impedance elementscomprises a resistor or a capacitor.
 17. The LED lamp of claim 15,wherein the current limiting circuit comprises at least a capacitor. 18.The LED lamp of claim 15, wherein the current limiting circuit comprisesa first capacitor, one end of the first capacitor being electricallyconnected to one pin of the first bi-pin terminal; and a secondcapacitor, one end of the second capacitor being electrically connectedto the other pin of the first bi-pin terminal.
 19. The LED lamp of claim15, wherein the first rectifier comprises two diodes electricallyconnected in series and a connection node connecting the two diodes iscoupled to the current limiting circuit.
 20. The LED lamp of claim 15,wherein the first rectifier comprises two diodes electrically connectedin series, and the first rectifier is electrically connected to thefirst filament-simulating circuit in parallel.